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Coordinate-system/139504: Find the domain of the function
f(x)=1
_____
x-4
1 solutions

Answer 101723 by jim_thompson5910(28536) About Me  on 2008-05-01 11:40:42 (Show Source):
You can put this solution on YOUR website!

f%28x%29=%281%29%2F%28x-4%29 Start with the given function


x-4=0 Set the denominator equal to zero. Remember, dividing by 0 is undefined. So if we find values of x that make the denominator zero, then we must exclude them from the domain.



x=0%2B4Add 4 to both sides


x=4 Combine like terms on the right side





Since x=4 makes the denominator equal to zero, this means we must exclude x=4 from our domain

So our domain is:

which in plain English reads: x is the set of all real numbers except x%3C%3E4

So our domain looks like this in interval notation


note: remember, the parenthesis excludes 4 from the domain

If we wanted to graph the domain on a number line, we would get:

Graph of the domain in blue and the excluded value represented by open circle

Notice we have a continuous line until we get to the hole at x=4 (which is represented by the open circle).
This graphically represents our domain in which x can be any number except x cannot equal 4


Equations/139536: -5(x-2)+3=5
1 solutions

Answer 101722 by jim_thompson5910(28536) About Me  on 2008-05-01 11:39:40 (Show Source):
You can put this solution on YOUR website!

-5%28x-2%29%2B3=5 Start with the given equation



-5x%2B10%2B3=5 Distribute


-5x%2B13=5 Combine like terms on the left side


-5x=5-13Subtract 13 from both sides


-5x=-8 Combine like terms on the right side


x=%28-8%29%2F%28-5%29 Divide both sides by -5 to isolate x



x=8%2F5 Reduce

--------------------------------------------------------------
Answer:
So our answer is x=8%2F5 (which is approximately x=1.6 in decimal form)


Coordinate-system/139503: Graph
3x-2y=-18
1 solutions

Answer 101721 by jim_thompson5910(28536) About Me  on 2008-05-01 11:38:59 (Show Source):
You can put this solution on YOUR website!

3x-2y=-18 Start with the given equation


-2y=-18-3x Subtract 3+x from both sides


-2y=-3x-18 Rearrange the equation


y=%28-3x-18%29%2F%28-2%29 Divide both sides by -2


y=%28-3%2F-2%29x%2B%28-18%29%2F%28-2%29 Break up the fraction


y=%283%2F2%29x%2B9 Reduce




Looking at y=%283%2F2%29x%2B9 we can see that the equation is in slope-intercept form y=mx%2Bb where the slope is m=3%2F2 and the y-intercept is b=9


Since b=9 this tells us that the y-intercept is .Remember the y-intercept is the point where the graph intersects with the y-axis

So we have one point




Now since the slope is comprised of the "rise" over the "run" this means
slope=rise%2Frun

Also, because the slope is 3%2F2, this means:

rise%2Frun=3%2F2


which shows us that the rise is 3 and the run is 2. This means that to go from point to point, we can go up 3 and over 2



So starting at , go up 3 units


and to the right 2 units to get to the next point



Now draw a line through these points to graph y=%283%2F2%29x%2B9

So this is the graph of y=%283%2F2%29x%2B9 through the points and


Quadratic_Equations/139519: What do I solve this by factoring?
20x^2 + 13x + 2
Thanks!
1 solutions

Answer 101720 by jim_thompson5910(28536) About Me  on 2008-05-01 11:34:57 (Show Source):
You can put this solution on YOUR website!

Looking at 20x%5E2%2B13x%2B2 we can see that the first term is 20x%5E2 and the last term is 2 where the coefficients are 20 and 2 respectively.

Now multiply the first coefficient 20 and the last coefficient 2 to get 40. Now what two numbers multiply to 40 and add to the middle coefficient 13? Let's list all of the factors of 40:



Factors of 40:
1,2,4,5,8,10,20,40

-1,-2,-4,-5,-8,-10,-20,-40 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to 40
1*40
2*20
4*10
5*8
(-1)*(-40)
(-2)*(-20)
(-4)*(-10)
(-5)*(-8)

note: remember two negative numbers multiplied together make a positive number


Now which of these pairs add to 13? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 13

First NumberSecond NumberSum
1401+40=41
2202+20=22
4104+10=14
585+8=13
-1-40-1+(-40)=-41
-2-20-2+(-20)=-22
-4-10-4+(-10)=-14
-5-8-5+(-8)=-13



From this list we can see that 5 and 8 add up to 13 and multiply to 40


Now looking at the expression 20x%5E2%2B13x%2B2, replace 13x with 5x%2B8x (notice 5x%2B8x adds up to 13x. So it is equivalent to 13x)

20x%5E2%2Bhighlight%285x%2B8x%29%2B2


Now let's factor 20x%5E2%2B5x%2B8x%2B2 by grouping:


%2820x%5E2%2B5x%29%2B%288x%2B2%29 Group like terms


5x%284x%2B1%29%2B2%284x%2B1%29 Factor out the GCF of 5x out of the first group. Factor out the GCF of 2 out of the second group


%285x%2B2%29%284x%2B1%29 Since we have a common term of 4x%2B1, we can combine like terms

So 20x%5E2%2B5x%2B8x%2B2 factors to %285x%2B2%29%284x%2B1%29


So this also means that 20x%5E2%2B13x%2B2 factors to %285x%2B2%29%284x%2B1%29 (since 20x%5E2%2B13x%2B2 is equivalent to 20x%5E2%2B5x%2B8x%2B2)



%285x%2B2%29%284x%2B1%29=0 Set the factorization equal to zero



Now set each factor equal to zero:
5x%2B2=0 or 4x%2B1=0

x=-2%2F5 or x=-1%2F4 Now solve for x in each case



--------------------------------
Answer:

So our solutions are

x=-2%2F5 or x=-1%2F4



Quadratic_Equations/139520: What do I solve this by factoring?
49x^2 - 14x - 3
Thanks!
1 solutions

Answer 101719 by jim_thompson5910(28536) About Me  on 2008-05-01 11:33:05 (Show Source):
You can put this solution on YOUR website!

Looking at 49x%5E2-14x-3 we can see that the first term is 49x%5E2 and the last term is -3 where the coefficients are 49 and -3 respectively.

Now multiply the first coefficient 49 and the last coefficient -3 to get -147. Now what two numbers multiply to -147 and add to the middle coefficient -14? Let's list all of the factors of -147:



Factors of -147:
1,3,7,21,49,147

-1,-3,-7,-21,-49,-147 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to -147
(1)*(-147)
(3)*(-49)
(7)*(-21)
(-1)*(147)
(-3)*(49)
(-7)*(21)

note: remember, the product of a negative and a positive number is a negative number


Now which of these pairs add to -14? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to -14

First NumberSecond NumberSum
1-1471+(-147)=-146
3-493+(-49)=-46
7-217+(-21)=-14
-1147-1+147=146
-349-3+49=46
-721-7+21=14



From this list we can see that 7 and -21 add up to -14 and multiply to -147


Now looking at the expression 49x%5E2-14x-3, replace -14x with 7x%2B-21x (notice 7x%2B-21x adds up to -14x. So it is equivalent to -14x)

49x%5E2%2Bhighlight%287x%2B-21x%29%2B-3


Now let's factor 49x%5E2%2B7x-21x-3 by grouping:


%2849x%5E2%2B7x%29%2B%28-21x-3%29 Group like terms


7x%287x%2B1%29-3%287x%2B1%29 Factor out the GCF of 7x out of the first group. Factor out the GCF of -3 out of the second group


%287x-3%29%287x%2B1%29 Since we have a common term of 7x%2B1, we can combine like terms

So 49x%5E2%2B7x-21x-3 factors to %287x-3%29%287x%2B1%29


So this also means that 49x%5E2-14x-3 factors to %287x-3%29%287x%2B1%29 (since 49x%5E2-14x-3 is equivalent to 49x%5E2%2B7x-21x-3)





%287x-3%29%287x%2B1%29=0 Set the factorization equal to zero



Now set each factor equal to zero:
7x-3=0 or 7x%2B1=0

x=3%2F7 or x=-1%2F7 Now solve for x in each case



-------------------------
Answer:

So our solutions are

x=3%2F7 or x=-1%2F7



Numeric_Fractions/139523: 4/5 = -11r - 2/3
1 solutions

Answer 101718 by jim_thompson5910(28536) About Me  on 2008-05-01 11:29:50 (Show Source):
You can put this solution on YOUR website!

4%2F5=-11r-2%2F3 Start with the given equation



%2815%29%284%2F5%29=%2815%29%28-11r-2%2F3%29 Multiply both sides by the LCM of 15. This will eliminate the fractions (note: if you need help with finding the LCM, check out this solver)



12=-165r-10 Distribute and multiply the LCM to each side



0=-165r-10-12Subtract 12 from both sides


%2B165r=-10-12 Add 165r to both sides


165r%2B0=-22 Combine like terms on the right side


r=%28-22%29%2F%28165%29 Divide both sides by 165 to isolate r



r=-2%2F15 Reduce

--------------------------------------------------------------
Answer:
So our answer is r=-2%2F15 (which is approximately r=-0.1333 in decimal form)



Graphs/139533: Graph the line with slope 1/2 passing through the point (-3,3) .
1 solutions

Answer 101717 by jim_thompson5910(28536) About Me  on 2008-05-01 11:28:24 (Show Source):
You can put this solution on YOUR website!

If you want to find the equation of line with a given a slope of 1%2F2 which goes through the point (-3,3), you can simply use the point-slope formula to find the equation:


---Point-Slope Formula---
y-y%5B1%5D=m%28x-x%5B1%5D%29 where m is the slope, and is the given point

So lets use the Point-Slope Formula to find the equation of the line

y-3=%281%2F2%29%28x--3%29 Plug in m=1%2F2, x%5B1%5D=-3, and y%5B1%5D=3 (these values are given)


y-3=%281%2F2%29%28x%2B3%29 Rewrite x--3 as x%2B3


y-3=%281%2F2%29x%2B%281%2F2%29%283%29 Distribute 1%2F2

y-3=%281%2F2%29x%2B3%2F2 Multiply 1%2F2 and 3 to get 3%2F2

y=%281%2F2%29x%2B3%2F2%2B3 Add 3 to both sides to isolate y

y=%281%2F2%29x%2B9%2F2 Combine like terms 3%2F2 and 3 to get 9%2F2 (note: if you need help with combining fractions, check out this solver)


------------------------------------------------------------------------------------------------------------
Answer:


So the equation of the line with a slope of 1%2F2 which goes through the point (-3,3) is:

y=%281%2F2%29x%2B9%2F2 which is now in y=mx%2Bb form where the slope is m=1%2F2 and the y-intercept is b=9%2F2

Notice if we graph the equation y=%281%2F2%29x%2B9%2F2 and plot the point (-3,3), we get (note: if you need help with graphing, check out this solver)

Graph of y=%281%2F2%29x%2B9%2F2 through the point (-3,3)
and we can see that the point lies on the line. Since we know the equation has a slope of 1%2F2 and goes through the point (-3,3), this verifies our answer.


Quadratic_Equations/139521: How would I solve this using quadratic formula?
f(x) = x^2 + 4

1 solutions

Answer 101716 by jim_thompson5910(28536) About Me  on 2008-05-01 11:26:57 (Show Source):
You can put this solution on YOUR website!
Let's use the quadratic formula to solve for x:


Starting with the general quadratic

ax%5E2%2Bbx%2Bc=0

the general solution using the quadratic equation is:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29



So lets solve x%5E2%2B4=0 (note: since the polynomial does not have an "x" term, the 2nd coefficient is zero. In other words, b=0. So that means the polynomial really looks like x%5E2%2B0%2Ax%2B4=0 notice a=1, b=0, and c=4)




x+=+%280+%2B-+sqrt%28+%280%29%5E2-4%2A1%2A4+%29%29%2F%282%2A1%29 Plug in a=1, b=0, and c=4



x+=+%280+%2B-+sqrt%28+0-4%2A1%2A4+%29%29%2F%282%2A1%29 Square 0 to get 0



x+=+%280+%2B-+sqrt%28+0%2B-16+%29%29%2F%282%2A1%29 Multiply -4%2A4%2A1 to get -16



x+=+%280+%2B-+sqrt%28+-16+%29%29%2F%282%2A1%29 Combine like terms in the radicand (everything under the square root)



x+=+%280+%2B-+4%2Ai%29%2F%282%2A1%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)



x+=+%280+%2B-+4%2Ai%29%2F%282%29 Multiply 2 and 1 to get 2



After simplifying, the quadratic has roots of

x=0+%2B+2%2Ai or x=0+-+2%2Ai

Notice if we graph the quadratic y=x%5E2%2B4, we get

+graph%28+500%2C+500%2C+-15%2C+15%2C+-11%2C+19%2C+x%5E2%2B4%29+ graph of y=x%5E2%2B4

And we can see that there are no real roots

To visually verify the answer, check out this page to see a visual representation of imaginary roots


Graphs/139531: This question is from textbook Essentials of College Mathematics
I still haven't received an answer and I have class tomorrow. Could someone please help me with graphing this equation?
What does the region look like and how do I graph it?
4x+3y=>24
3x+4y=>8
x=>0
y=>0
I would appreciate your help as soon as possible.
Anne
1 solutions

Answer 101715 by jim_thompson5910(28536) About Me  on 2008-05-01 11:24:05 (Show Source):
You can put this solution on YOUR website!

Start with the given system of inequalities
4x%2B3y%3E=24
3x%2B4y%3E=8
x%3E=0
y%3E=0

In order to graph this system of inequalities, we need to graph each inequality one at a time.


First lets graph the first inequality 4x%2B3y%3E=24
In order to graph 4x%2B3y%3E=24, we need to graph the equation 4x%2B3y=24 (just replace the inequality sign with an equal sign).
So lets graph the line 4x%2B3y=24 (note: if you need help with graphing, check out this solver)
+graph%28+500%2C+500%2C+-20%2C+20%2C+-20%2C+20%2C+-%284%2F3%29x%2B8%29+ graph of 4x%2B3y=24
Now lets pick a test point, say (0,0). Any point will work, (just make sure the point doesn't lie on the line) but this point is the easiest to work with. Now evaluate the inequality 4x%2B3y%3E=24 with the test point

Substitute (0,0) into the inequality
4%280%29%2B3%280%29%3E=24 Plug in x=0 and y=0
0%3E=24 Simplify



(note: for some reason, some of the following images do not display correctly in Internet Explorer. So I recommend the use of
Firefox to see these images.)


Since this inequality is not true, we do not shade the entire region that contains (0,0). So this means we shade the region that is on the opposite side of the line
Graph of 4x%2B3y%3E=24 with the boundary (which is the line 4x%2B3y=24 in red) and the shaded region (in green)

---------------------------------------------------------------


Now lets graph the second inequality 3x%2B4y%3E=8
In order to graph 3x%2B4y%3E=8, we need to graph the equation 3x%2B4y=8 (just replace the inequality sign with an equal sign).
So lets graph the line 3x%2B4y=8 (note: if you need help with graphing, check out this solver)
+graph%28+500%2C+500%2C+-20%2C+20%2C+-20%2C+20%2C+-%283%2F4%29x%2B2%29+ graph of 3x%2B4y=8
Now lets pick a test point, say (0,0). Any point will work, (just make sure the point doesn't lie on the line) but this point is the easiest to work with. Now evaluate the inequality 3x%2B4y%3E=8 with the test point

Substitute (0,0) into the inequality
3%280%29%2B4%280%29%3E=8 Plug in x=0 and y=0
0%3E=8 Simplify



Since this inequality is not true, we do not shade the entire region that contains (0,0). So this means we shade the region that is on the opposite side of the line
Graph of 3x%2B4y%3E=8 with the boundary (which is the line 3x%2B4y=8 in red) and the shaded region (in green)

---------------------------------------------------------------


Now lets graph the third inequality x%3E=0
In order to graph x%3E=0, we need to graph the equation x=0 (just replace the inequality sign with an equal sign).
So lets graph the line x=0 (simply draw a vertical line through x=0)
+graph%28+500%2C+500%2C+-20%2C+20%2C+-20%2C+20%2C+1000%28x-0%29%29+ graph of x=0 (note:the graph is the line that is overlapping the y-axis. So it may be hard to see)
Now lets pick a test point, say (1,0). Any point will work, (just make sure the point doesn't lie on the line) but this point is the easiest to work with. Now evaluate the inequality x%3E=0 with the test point

Substitute (1,0) into the inequality
%281%29%3E=0 Plug in x=1 and y=0
1%3E=0 Simplify



Since this inequality is true, we simply shade the entire region that contains (1,0)
Graph of x%3E=0 with the boundary (which is the line x=0 in red) and the shaded region (in green)

---------------------------------------------------------------


Now lets graph the fourth inequality y%3E=0
In order to graph y%3E=0, we need to graph the equation y=0 (just replace the inequality sign with an equal sign).
So lets graph the line y=0 (simply draw a horizontal line through y=0)
+graph%28+500%2C+500%2C+-20%2C+20%2C+-20%2C+20%2C+0%29+ graph of y=0 (note:the graph is the line that is overlapping the x-axis. So it may be hard to see)
Now lets pick a test point, say (0,1). Any point will work, (just make sure the point doesn't lie on the line) but this point is the easiest to work with. Now evaluate the inequality y%3E=0 with the test point

Substitute (0,1) into the inequality
%281%29%3E=0 Plug in x=0 and y=1
1%3E=0 Simplify



Since this inequality is true, we simply shade the entire region that contains (0,1)
Graph of y%3E=0 with the boundary (which is the line y=0 in red) and the shaded region (in green)

---------------------------------------------------------------


So we essentially have these 4 regions:

Region #1
Graph of 4x%2B3y%3E=24


Region #2
Graph of 3x%2B4y%3E=8


Region #3
Graph of x%3E=0


Region #4
Graph of y%3E=0




When these inequalities are graphed on the same coordinate system, the regions overlap to produce this region. It's a little hard to see, but after evenly shading each region, the intersecting region will be the most shaded in.







Here is a cleaner look at the intersection of regions




Here is the intersection of the 4 regions represented by the series of dots


Linear-equations/139482: Find the distance between (5,8) and (-4,5)
1 solutions

Answer 101690 by jim_thompson5910(28536) About Me  on 2008-04-30 23:56:39 (Show Source):
You can put this solution on YOUR website!
Start with the given distance formula
d=sqrt%28%28x%5B1%5D-x%5B2%5D%29%5E2%2B%28y%5B1%5D-y%5B2%5D%29%5E2%29 where is the first point and is the second point

d=sqrt%28%285--4%29%5E2%2B%288-5%29%5E2%29 Plug in x%5B1%5D=5, x%5B2%5D=-4, y%5B1%5D=8, y%5B2%5D=5

d=sqrt%28%289%29%5E2%2B%283%29%5E2%29 Evaluate 5--4 to get 9. Evaluate 8-5 to get 3.

d=sqrt%2881%2B9%29 Square each value

d=sqrt%2890%29 Add

d=3%2Asqrt%2810%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)


So the distance approximates to

d=9.48683298050514

which rounds to
9.49

So the distance between (5,8) and (-4,5) is approximately 9.49 units


Exponential-and-logarithmic-functions/139457: Find the largest value of x that satisfies:
log(base5) (x^2) − log(base5) (x+2) = 2
x =
THANKS A LOT!
1 solutions

Answer 101689 by jim_thompson5910(28536) About Me  on 2008-04-30 23:33:53 (Show Source):
You can put this solution on YOUR website!
log%285%2C%28x%5E2%29%29-log%285%2C%28x%2B2%29%29+=+2+ Start with the given equation


log%285%2Cx%5E2%2F%28x%2B2%29%29+=+2+ Combine the logs


x%5E2%2F%28x%2B2%29+=+5%5E2+ Use the relationship log%28b%2C%28y%29%29=x <===> b%5Ex=y to rewrite the equation


x%5E2%2F%28x%2B2%29+=+25+ Square 5


x%5E2+=+25%28x%2B2%29+ Multiply both sides by x%2B2


x%5E2+=+25x%2B50+ Distribute


x%5E2-25x-50=0++ Get all terms to one side


Let's use the quadratic formula to solve for x:


Starting with the general quadratic

ax%5E2%2Bbx%2Bc=0

the general solution using the quadratic equation is:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29



So lets solve x%5E2-25%2Ax-50=0 ( notice a=1, b=-25, and c=-50)




x+=+%28--25+%2B-+sqrt%28+%28-25%29%5E2-4%2A1%2A-50+%29%29%2F%282%2A1%29 Plug in a=1, b=-25, and c=-50



x+=+%2825+%2B-+sqrt%28+%28-25%29%5E2-4%2A1%2A-50+%29%29%2F%282%2A1%29 Negate -25 to get 25



x+=+%2825+%2B-+sqrt%28+625-4%2A1%2A-50+%29%29%2F%282%2A1%29 Square -25 to get 625 (note: remember when you square -25, you must square the negative as well. This is because %28-25%29%5E2=-25%2A-25=625.)



x+=+%2825+%2B-+sqrt%28+625%2B200+%29%29%2F%282%2A1%29 Multiply -4%2A-50%2A1 to get 200



x+=+%2825+%2B-+sqrt%28+825+%29%29%2F%282%2A1%29 Combine like terms in the radicand (everything under the square root)



x+=+%2825+%2B-+5%2Asqrt%2833%29%29%2F%282%2A1%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)



x+=+%2825+%2B-+5%2Asqrt%2833%29%29%2F2 Multiply 2 and 1 to get 2

So now the expression breaks down into two parts

x+=+%2825+%2B+5%2Asqrt%2833%29%29%2F2 or x+=+%2825+-+5%2Asqrt%2833%29%29%2F2




So these expressions approximate to

x=26.861 or x=-1.861



So we can clearly see that x=26.861 is the largest value of x that satisfies the equation


Circles/139417: How do I solve for x with the information given?
Photobucket
1 solutions

Answer 101688 by jim_thompson5910(28536) About Me  on 2008-04-30 23:25:44 (Show Source):
You can put this solution on YOUR website!
Notice how the drawing has one angle that is not labeled. This angle and angle "x" are vertical angles. So this means that the unlabeled angle is also "x". So in the drawing write in this angle.


Since there are 360 degrees in a circle, this means that the sum of these angles is 360. So we have the equation

100%2Bx%2B160%2Bx=360





2x%2B260=360 Combine like terms on the left side


2x=360-260Subtract 260 from both sides


2x=100 Combine like terms on the right side


x=%28100%29%2F%282%29 Divide both sides by 2 to isolate x



x=50 Divide

--------------------------------------------------------------
Answer:
So our answer is x=50


Quadratic_Equations/139443: Solve then graph.
x + 8 > 2
The solution set is ?
Help me figure this one out please.
I would like to thank everyone who has helped me. I still have a couple weeks of needing your help. I must say I have learned a lot, but am still confused of a lot also...Thanks again everyone.
1 solutions

Answer 101687 by jim_thompson5910(28536) About Me  on 2008-04-30 23:20:30 (Show Source):
You can put this solution on YOUR website!

x%2B8%3E2 Start with the given inequality



x%3E2-8Subtract 8 from both sides


x%3E-6 Combine like terms on the right side

--------------------------------------------------------------
Answer:
So our answer is x%3E-6



Now let's graph the solution set





Start with the given inequality


Plot the point x=-6 on a number line

number_line%28+500%2C+-16%2C+4%2C+-6+%29


Now plug in x=0 into the inequality





Since is true, this means that we shade the entire region that x=0 is in.


So shade to the right of x=-6 . Note: there is a open circle at x=-6



Linear-systems/139472: This question is from textbook College Algebra
How can I solve this system?
3x+4y=29
-x+2y=7
1 solutions

Answer 101686 by jim_thompson5910(28536) About Me  on 2008-04-30 23:17:40 (Show Source):
You can put this solution on YOUR website!
Let's solve this system using elimination


Start with the given system of equations:

system%283x%2B4y=29%2C-x%2B2y=7%29



Now in order to solve this system by using elimination/addition, we need to solve (or isolate) one variable. I'm going to solve for y.





In order to solve for one variable, we must eliminate the other variable. So if we wanted to solve for y, we would have to eliminate x (or vice versa).


So lets eliminate x. In order to do that, we need to have both x coefficients that are equal in magnitude but have opposite signs (for instance 2 and -2 are equal in magnitude but have opposite signs). This way they will add to zero. By adding to zero, they can be eliminated.



So to make the x coefficients equal in magnitude but opposite in sign, we need to multiply both x coefficients by some number to get them to an common number. So if we wanted to get 3 and -1 to some equal number, we could try to get them to the LCM.



Since the LCM of 3 and -1 is 3, we need to multiply both sides of the top equation by 1 and multiply both sides of the bottom equation by 3 like this:




1%283x%2B4y%29=1%2829%29 Multiply the top equation (both sides) by 1
3%28-x%2B2y%29=3%287%29 Multiply the bottom equation (both sides) by 3




Distribute and multiply

3x%2B4y=29
-3x%2B6y=21


Now add the equations together. In order to add 2 equations, group like terms and combine them

%283x-3x%29%2B%284y%2B6y%29=29%2B21

Combine like terms and simplify



cross%283x-3x%29%2B10y=50 Notice how the x terms cancel out




10y=50 Simplify




y=50%2F10 Divide both sides by 10 to isolate y




y=5 Reduce



Now plug this answer into the top equation 3x%2B4y=29 to solve for x

3x%2B4y=29 Start with the first equation



3x%2B4%285%29=29 Plug in y=5




3x%2B20=29 Multiply



3x=29-20Subtract 20 from both sides


3x=9 Combine like terms on the right side


x=%289%29%2F%283%29 Divide both sides by 3 to isolate x



x=3 Divide




So our answer is
x=3 and y=5



which also looks like




Now let's graph the two equations (if you need help with graphing, check out this solver)


From the graph, we can see that the two equations intersect at . This visually verifies our answer.




graph of 3x%2B4y=29 (red) and -x%2B2y=7 (green) and the intersection of the lines (blue circle).




Exponential-and-logarithmic-functions/139463: This question is from textbook College Algebra
Hello, I worked this problem and only got half credit.
How can I work this as a systems of equations
y=x^2-4
x-y=-2
This is what I did
x=y-2
y=(y-2)^2-4
2y-4-4=0

1 solutions

Answer 101685 by jim_thompson5910(28536) About Me  on 2008-04-30 23:14:54 (Show Source):
You can put this solution on YOUR website!
Start with the given system
y=x%5E2-4
x-y=-2


x=y-2 Solve for x in the second equation


y=%28y-2%29%5E2-4 Plug in x=y-2


y=y%5E2-4y%2B4-4 Foil


0=y%5E2-4y%2B4-4-y Subtract y from both sides


0=y%5E2-5y Combine like terms


0=y%28y-5%29 Factor the right side




Now set each factor equal to zero:
y=0 or y-5=0

y=0 or y=5 Now solve for y in each case


So our y-values are

y=0 or y=5


Let's find x when y=0

x=y-2 Start with the second equation


x=0-2 Plug in y=0


x=-2 Subtract


So when x=-2 then y=0



Let's find x when y=5

x=y-2 Start with the second equation


x=5-2 Plug in y=5


x=3 Subtract


So when x=3 then y=5




-----------------------------------

Answer:

So the solutions are

(-2,0) or (3,5)


Parallelograms/139411: I know I'm solving for x, so I think I set up the equation like
(2x+5)+(3x+1)+(13)+(5x-7)=? My problem is that I don't know what I set it to equal to.
Photobucket
1 solutions

Answer 101657 by jim_thompson5910(28536) About Me  on 2008-04-30 20:10:37 (Show Source):
You can put this solution on YOUR website!
Since the diagonals of a rectangle are equal, this means that we have the equation

%282x%2B5%29%2B%285x-7%29=%283x%2B1%29%2B%2813%29


2x%2B5%2B5x-7=3x%2B1%2B13 Remove the parenthesis



7x-2=3x%2B1%2B13 Combine like terms on the left side


7x-2=3x%2B14 Combine like terms on the right side


7x=3x%2B14%2B2Add 2 to both sides


7x-3x=14%2B2 Subtract 3x from both sides


4x=14%2B2 Combine like terms on the left side


4x=16 Combine like terms on the right side


x=%2816%29%2F%284%29 Divide both sides by 4 to isolate x



x=4 Divide

--------------------------------------------------------------
Answer:
So our answer is x=4







Functions/138844: k. What price would you sell the tile sets at to realize this profit (hint, use the demand equation from part a)?
1 solutions

Answer 101293 by jim_thompson5910(28536) About Me  on 2008-04-27 16:46:55 (Show Source):
You can put this solution on YOUR website!
From part a), we found the demand equation p=-x%2B62 where x is the number of units sold and p is the price.


To find the demand simply plug in x=28 (remember, we max out the profit when 28 tiles are sold)


p=-x%2B62 Start with the given equation


p=-28%2B62 Plug in x=28


p=34 Add


So the price should be set at $34


Trigonometry-basics/138826: Write sin%287x%29cos%285x%29 as a sum


Write cos%287x%29-sin%285x%29+ as a product
1 solutions

Answer 101283 by jim_thompson5910(28536) About Me  on 2008-04-27 14:46:01 (Show Source):
You can put this solution on YOUR website!
1)

Start with the given expression


Use the Product-to-Sum formula


Add/Subtract


Distribute



So






2)

Are you sure that it's cos%287x%29-sin%285x%29+? There are no corresponding sum-to-product identities for mixed the trig functions sine and cosine.

Double check your assignment.


Trigonometry-basics/138824: Solve %28sin%28x%2F2%29%29%5E2-%28sin%28x%29%29%5E2=0
1 solutions

Answer 101281 by jim_thompson5910(28536) About Me  on 2008-04-27 14:38:55 (Show Source):
You can put this solution on YOUR website!
Start with the given equation



Let . So this means that



Replace with u and with 2u


Rewrite as


Replace with





Square



Factor out



Now use the zero product property:


...or...


Now let's solve :





Take the square root of both sides


...or... Take the arcsine of both sides


Since , this means


...or...



However, since is not in the interval [0,2), it is not a solution.


So the first solution is



--------------------------------------------------------------------

Now let's solve :





Subtract 1 from both sides


Divide both sides by -4


Take the square root of both sides:
...or...


So let's solve the first part :





...or...


...or...


However since our interval is positive, the negative answer is not in the interval.


So another part of the solution is



---------------------


Now let's solve the second part :






...or...


...or...



So another part of the solution is




===============================================

Answer:


So all together our solutions are:



Trigonometry-basics/138823: Find the exact value of cos%28%281%2F2%29cos%5E%28-1%29%28%28-3%29%2F4%29%29
1 solutions

Answer 101279 by jim_thompson5910(28536) About Me  on 2008-04-27 14:35:46 (Show Source):
You can put this solution on YOUR website!
let




so




Substitute "2u" in for "u"


Multiply


Take the arccosine of the cosine of -3%2F4 to get -3%2F4


Replace with


Add 1 to both sides


Divide both sides by 2


Take the square root of both sides


Simplify


Rationalize the denominator if necessary



So



Trigonometry-basics/138821: Prove the identity: sin%283x%29+=+3%2Asin%28x%29+%96+4%2A%28sin%28x%29%29%5E3 (x is theta)
1 solutions

Answer 101276 by jim_thompson5910(28536) About Me  on 2008-04-27 14:25:07 (Show Source):
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Note: I'm only manipulating the left side. I'm not touching the right side. I'm only showing it for comparison.


Start with the given equation


Break up to get


Expand using the sum-difference formulas


Replace with . Replace with .


Factor out


Rearrange the terms


Factor out 2


Replace with


Replace with


Distribute


Combine like terms


Distribute




So we've just proven that



is an identity.


Trigonometry-basics/138819: Prove the identity: sin%28a+%2B+B%29+sin+%28a-B%29+=+%28sin%28a%29%29%5E2-%28sin%28B%29%29%5E2 (x is theta)
1 solutions

Answer 101275 by jim_thompson5910(28536) About Me  on 2008-04-27 14:16:58 (Show Source):
You can put this solution on YOUR website!
Note: I'm only manipulating the left side. I'm not touching the right side. I'm only showing it for comparison.



Start with the given equation


Expand by using the Sum-Difference Formulas


Foil


Combine like terms


Replace with . Replace with




Distribute


Combine like terms




So we've just proven that



is an identity.


Trigonometry-basics/138815: Prove the identity: tan%28x%29+%2F%28+1+%2B+%28tan%28x%29%29%5E2%29+=+sin%28x%29cos%28x%29 (x is theta)
1 solutions

Answer 101273 by jim_thompson5910(28536) About Me  on 2008-04-27 14:08:28 (Show Source):
You can put this solution on YOUR website!
Note: I'm only manipulating the left side. I'm not touching the right side. I'm only showing it for comparison.




Start with the given equation




Replace with


Simplify


Multiply both the numerator and denominator by the LCD . This will clear out the denominators in both the numerator and the denominator.



Distribute and multiply




Replace with 1



Simplify


So we've just proven that



is an identity.


Trigonometry-basics/138801: Graph y=-%281%2F2%29tan%282x+%2B+pi%2F2%29 and the period and phase shift
1 solutions

Answer 101260 by jim_thompson5910(28536) About Me  on 2008-04-27 12:41:30 (Show Source):
You can put this solution on YOUR website!
Graph of y=-%281%2F2%29tan%282x+%2B+pi%2F2%29 (not the best graph, but it gives you an idea of what it looks like)




Remember the general form is y=a%2Atan%28bx%2Bc%29%2Bd where the period is pi%2Fabs%28b%29, and the phase shift is -c%2Fb



So in this case...

the period is pi%2F2, the phase shift is -%28pi%2F2%29%2F2=%28-pi%2F2%29%281%2F2%29=-pi%2F4




Trigonometry-basics/138798: Graph y=2sin%283x-pi%2F2%29 and find amplitude, period and phase shift
1 solutions

Answer 101259 by jim_thompson5910(28536) About Me  on 2008-04-27 12:36:21 (Show Source):
You can put this solution on YOUR website!
Graph of y=2sin%283x-pi%2F2%29
+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C2sin%283x-pi%2F2%29++++%29+


Remember the general form is y=a%2Asin%28bx%2Bc%29%2Bd where the amplitude is abs%28a%29, the period is 2pi%2Fabs%28b%29, and the phase shift is -c%2Fb



So in this case...

the amplitude is a=2, the period is 2pi%2F3, the phase shift is -%28-pi%2F2%29%2F3=%28pi%2F2%29%281%2F3%29=pi%2F6




Functions/138710: "A company calculates it's profit by finding the difference between
revenue and cost. The cost function of producing x hammers is C(x) =
4x+170. If each hammer is sold for $10, the revenue function for
selling x hammers is R (x) = 10x."

1.) How many hammers must be sold to make a profit?

2.) How many hammers must be sold to make a profit of $100?



1 solutions

Answer 101212 by jim_thompson5910(28536) About Me  on 2008-04-26 17:58:25 (Show Source):
You can put this solution on YOUR website!
1)


The profit function is defined by:

Profit = Revenue - Cost



So in function notation it looks like:

P%28x%29=R%28x%29-C%28x%29


So in our case:

P%28x%29=10x-%284x%2B170%29 Plug in R%28x%29=10x and C%28x%29=4x%2B170


P%28x%29=10x-4x-170 Distribute the negative


P%28x%29=6x-170 Combine like terms


6x-170%3E0 Set the right side greater than zero. Remember we're looking for positive profit.


6x%3E170 Add 170 to both sides


x%3E170%2F6 Divide both sides by 6


x%3E28.333 Divide


x%3E29 Round to the nearest whole number. A third of a hammer can't be sold.



So when x%3E29, we'll have positive profit. So more than 29 hammers must be sold to gain a profit.







2)

We're still using the profit function. So P%28x%29=6x-170


Since we want a profit of $100, simply plug in P%28x%29=100.


P%28x%29=6x-170 Start with the profit function


100=6x-170 Plug in P%28x%29=100


270=6x Add 170 to both sides


45=x Divide both sides by 6


So when x=45, we'll have a profit of $100. So 45 must be sold to make a profit of $100.


Graphs/138691: Is the equation y%5E4%2By%5E2-7=3x%2B5x%5E2 symmetric about the x-axis?
1 solutions

Answer 101206 by jim_thompson5910(28536) About Me  on 2008-04-26 14:41:38 (Show Source):
You can put this solution on YOUR website!
Remember, if f%28x%29=-f%28x%29, then the equation is symmetric about the x-axis. So in this case, we only need to replace y with negative y and see if the equations are equivalent.

y%5E4%2By%5E2-7=3x%2B5x%5E2 Start with the given equation


%28-y%29%5E4%2B%28-y%29%5E2-7=3x%2B5x%5E2 Replace each "y" with negative y


y%5E4%2By%5E2-7-7=3x%2B5x%5E2 Raise -y to the fourth power to get y%5E4. Raise -y to the second power to get y%5E2

Since the first equation y%5E4%2By%5E2-7=3x%2B5x%5E2 is equivalent to the last equation, this shows that graph is symmetric about the x-axis


For visual proof, here's the graph:





From the graph, we can see that equation is symmetric about the x-axis


Graphs/138688: The demand equation is given as y=x%2F50%2B15 and the supply as y=12500%2Fx. Find the equilibrium price.
1 solutions

Answer 101205 by jim_thompson5910(28536) About Me  on 2008-04-26 14:31:24 (Show Source):
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Start with the given system

system%28y=x%2F50%2B15%2Cy=12500%2Fx%29


y=12500%2Fx Now move onto the second equation


x%2F50%2B15=12500%2Fx Plug in y=x%2F50%2B15


50x%28x%2F50%2B15%29=50x%2812500%2Fx%29 Multiply both sides by the LCD 50x


x%5E2%2B750x=625000 Distribute and multiply


x%5E2%2B750x-625000=0 Subtract 625000 from both sides.



%28x%2B1250%29%28x-500%29=0 Factor the left side (note: if you need help with factoring, check out this solver)



Now set each factor equal to zero:
x%2B1250=0 or x-500=0

x=-1250 or x=500 Now solve for x in each case


So our answer is
x=-1250 or x=500


However, a negative number of jackets does not make sense. So the only solution is x=500


250=12500%2F500 Now plug x=500 into the second equation



So our solution is x=500 and y=25

So when 500 jackets are sold, the supply will equal the demand at $25.


Graphs/138687: Graph the two equations x%5E2%2By%5E2=26 and y=-x%2B8 and find the solutions
1 solutions

Answer 101203 by jim_thompson5910(28536) About Me  on 2008-04-26 14:21:22 (Show Source):
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x%5E2%2By%5E2=26 Start with the given equation


y=0%2B-sqrt%2826-x%5E2%29 Solve for y


y=sqrt%2826-x%5E2%29 or y=-sqrt%2826-x%5E2%29 Break up the right side



Now let's graph sqrt%2826-x%5E2%29

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+sqrt%2826-x%5E2%29+%29+ Graph of y=sqrt%2826-x%5E2%29


Now let's graph -sqrt%2826-x%5E2%29

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+-sqrt%2826-x%5E2%29+%29+ Graph of y=-sqrt%2826-x%5E2%29


Now graph y=-x%2B8

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+-x%2B8++%29+ Graph of y=-x%2B8


Now graph the three equations together (note: the first two equations make up x%5E2%2By%5E2=26 )

Graph of y=sqrt%2826-x%5E2%29 (red). Graph of y=sqrt%2826-x%5E2%29 (green). Graph of y=-x%2B8(blue)


From the graph, we can see that there are no intersections. So there are no solutions.


Graphs/138686: Graph the two equations y=x%5E2%2B2x%2B1 and y=x%2B3 and find the solutions
1 solutions

Answer 101201 by jim_thompson5910(28536) About Me  on 2008-04-26 14:12:50 (Show Source):
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First graph y=x%5E2%2B2x%2B1

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+x%5E2%2B2x%2B1++%29+ Graph of y=x%5E2%2B2x%2B1



Now graph y=x%2B3

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+x%2B3++%29+ Graph of y=x%2B3


Now graph the two equations together

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+10%2C+x%5E2%2B2x%2B1%2Cx%2B3++%29+ Graph of y=x%5E2%2B2x%2B1 (red. Graph of y=x%2B3(green)


From the graph, we can see that the two equations intersect at the points (-2,1) and (1,4)


So this means that the solutions are
x=-2 and y=1

OR

x=1 and y=4


Graphs/138685: A cost function is given as C%28x%29=%281%2F2%29x%5E3-8x%5E2-80x%2B200. Find the cost of producing 100 boxes
1 solutions

Answer 101199 by jim_thompson5910(28536) About Me  on 2008-04-26 14:00:53 (Show Source):
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Since we're trying to find C%28100%29, our test zero is 100


Now set up the synthetic division table by placing the test zero in the upper left corner and placing the coefficients of the numerator to the right of the test zero.
100| 1/2 -8-80200
|



Start by bringing down the leading coefficient (it is the coefficient with the highest exponent which is 1)
100| 1/2 -8-80200
|
1/2




Multiply 100 by 1/2 and place the product (which is 50) right underneath the second coefficient (which is -8)
100| 1/2 -8-80200
| 50
1/2



Add 50 and -8 to get 42. Place the sum right underneath 50.
100| 1/2 -8-80200
| 50
1/2 42




Multiply 100 by 42 and place the product (which is 4200) right underneath the third coefficient (which is -80)
100| 1/2 -8-80200
| 50 4200
1/2 42 4120




Add 4200 and -80 to get 4120. Place the sum right underneath 4200.
100| 1/2 -8-80200
| 50 4200
1/2 42 4120




Multiply 100 by 4120 and place the product (which is 412000) right underneath the fourth coefficient (which is 200)
100| 1/2 -8-80200
| 50 4200 412000
1 42 4120




Add 412000 and 200 to get 412200. Place the sum right underneath 412000.
100| 1/2 -8-80200
| 50 4200 412000
1/2 42 4120 412200





Since the last column adds to 412200, we have a remainder of 412200.



------------------------------------

Answer:

So according to the remainder theorem, C%28100%29=412200


So the cost to produce 100 boxes is $412,200