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Recent problems solved by 'sophxmai'

sophxmai answered: 60 problems
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Polynomials-and-rational-expressions/619242: (12w^4- 6w³+w²)/3w²
1 solutions

Answer 389568 by sophxmai(60) About Me  on 2012-06-09 23:57:45 (Show Source):
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(12w^4- 6w³+w²)/3w² can be rewritten as
12w^4/3x^2 - 6w^3/3w^2 + w^2/3w^2

So just simplify the fractions.
12w^4/3x^2 - 6w^3/3w^2 + w^2/3w^2
=4w^2-2w+1/3


Linear-systems/619345: Factor the trinomial
18r^3-39r^2+20r
1 solutions

Answer 389566 by sophxmai(60) About Me  on 2012-06-09 23:54:17 (Show Source):
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18r^3-39r^2+20r
Factor out an r
r(18r^2-39r+20)
=r(3r-4)(6r-5)


logarithm/619317: Solve the logarithmic equation: log(x+1)+log(x-1)=log3
1 solutions

Answer 389563 by sophxmai(60) About Me  on 2012-06-09 23:48:18 (Show Source):
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Using the rule loga+logb=logab

log(x+1)+log(x-1)=log3
log[(x+1)*(x-1)]=log3
log(x^2-x+x-1)=log3
log(x^2-1)=log3
10^[log(x^2-1)]=10^log3
x^2-1=3
x^2=4
x=sqrt4
x=+2,-2


Expressions-with-variables/619347: if it cost $78.86 to buy 3 tickets in japan plus 2 tickets in switzerlan. 3 tickets in switzerland plus 2 tickets in japan cost $74.84. how much does an average movie ticket cost in each country?
1 solutions

Answer 389562 by sophxmai(60) About Me  on 2012-06-09 23:45:45 (Show Source):
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x=Japan
y=Switzerland

3x+2y=78.86
2x+3y=74.84
Find x and y

Multiply each equation to cancel one of the variables out.
3x+2y=78.86 x2
6x+4y=157.72

2x+3y=74.84 x3
6x+9y=224.52

Now the two equations have 6x, and if you subtract one from the other, you can cancel out one of the variables.
6x+4y=157.72
6x+9y=224.52

-5y=-66.8
y=-66.8/-5
y=13.36

Now you have y, substitute y into an equation to find x.
2x+3y=74.84
2x+3(13.36)=74.84
2x+40.08=74.84
2x=34.76
x=34.76/2
x=17.38

So tickets in Japan cost $17.38 and tickets in Switzerland cost $13.36


Probability-and-statistics/619296: If 11 coins are tossed what is the probability of getting EXACTLY 2 heads?
1 solutions

Answer 389561 by sophxmai(60) About Me  on 2012-06-09 23:37:06 (Show Source):
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If 11 coins are tossed what is the probability of getting EXACTLY 2 heads?
Use P(x=k)=nCk*p^k*q^(n-k)
Where p=probability of success and q=1-p, probability of failure

So
P(x=2)=(11C2)(1/2)^2(1/2)^(11-2)
=(11C2)(1/4)(1/512)
=(11C2)(1/2048)
=0.0269


Probability-and-statistics/619298: A 5-card hand is dealt from a deck of 52 cards. What is the probability that
a.) none are queens?
b.) all are queens?
1 solutions

Answer 389560 by sophxmai(60) About Me  on 2012-06-09 23:31:28 (Show Source):
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There are only 4 queens in a deck of cards.
P(a)= probability that event A occurs
= (total number of desired outcomes)/(total number of possible outcomes)
Use combinatorics.

The total number of possible outcomes in a) and b) is
52C5 = 2598960

The total number of desired outcomes in a) is
48C5 = 1712304
It's 48 because you don't want any queens, and there are 4 queens in a deck of 52

The total number of desired outcomes in b) is
0 because there are only 4 queens in a deck of 52, but you want your 5 card hand to be all queens.

So
a)P(no queens in a 5 card hand)=1712304/2598960=0.659
b)P(all queens in a 5 card hand)=0/2598960=0


Graphs/619250: find the slope of the line containing (3,5) and (1,8)

1 solutions

Answer 389559 by sophxmai(60) About Me  on 2012-06-09 23:18:21 (Show Source):
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Your points are (3,5) and (1,8)
Use the slope formula: m=(y2-y1)/(x2-x1)

m=(8-5)/(1-3)
m=3/-2
m=-3/2


Probability-and-statistics/619301: A 5-card hand is dealt from a deck of 52 cards. What is the probability that exactly one card is a king?
1 solutions

Answer 389558 by sophxmai(60) About Me  on 2012-06-09 23:03:43 (Show Source):
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Probability is (total number of desired outcomes)/(total number of possibly outcomes)

Desired outcome: you want 1 king, and 4 other cards

To get that, you use combinatorics:
4C1 x 48C4 = 778320

Total outcome: 5 card hand

To get that, you do 52C5 = 2598960

Then the probability is
P(1 king in a 5 card hand)= 778320 / 2598960 = 0.299


Inequalities/614742: Graph the inequality. 2x-7y>14 Determine if the graph is solid or dotted, and shaded above or below:
1 solutions

Answer 386687 by sophxmai(60) About Me  on 2012-05-25 05:04:40 (Show Source):
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2x-7y>14
Determine if the graph is solid or dotted, and shaded above or below.

First off, the graph is dotted. You can tell this because the inequality sign is greater/less than. If the sign was greater/less than or equal to, then the graph would be a solid.

To determine whether the graph is shaded above or below, you must first solve for y, and graph it.
2x-7y%3E14
2x-14%3E7y
%282%2F7%29x-%2814%2F7%29%3Ey
%282%2F7%29x-2%3Ey

So the equation is y%3C%282%2F7%29x-2
To graph this, look at it with an equal sign instead. y=%282%2F7%29x-2
This has a y-intercept of -2, and a slope of 2/7.

Now to determine what part is shaded, look at the equation that is solved for y, and pay attention to the inequality sign. If it is y>... then it is shaded above. If it is y<... then it is shaded below. In this case, it is shaded below.


Exponents-negative-and-fractional/614754: can you please help me with this?
(8 + 5)^0 => => is it 1 because anything with an exponent of zero is 1 am i correct?

1 solutions

Answer 386686 by sophxmai(60) About Me  on 2012-05-25 04:51:52 (Show Source):
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Yes that's right, anything to the power of 0 is 1.


Exponential-and-logarithmic-functions/614548: Solve for x:+2%283%5Ex%29+=+7%285%5Ex%29+
1 solutions

Answer 386601 by sophxmai(60) About Me  on 2012-05-24 15:22:04 (Show Source):
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take the log of both sides and then separate the 2(3^x) by the log(m)+log(n)=log(mn) rule.

+2%283%5Ex%29+=+7%285%5Ex%29+
log(2(3^x))=log(7(5^x))
log(2)+log(3^x)=log(7)+log(5^x)
log(2)+xlog(3)=log(7)+xlog(5)
xlog(3)-xlog(5)=log(7)-log(2)
x(log(3)-log(5))=log(7)-log(2)
x=(log(7)-log(2))/(log(3)-log(5))
x=-2.452427 <--i used a calculator

x=(log(7)-log(2))/(log(3)-log(5)) can be rewritten using the rule log(m)-log(n)=log(m/n)
x=log(7/2)/log(3/5)


Linear-systems/614544: 2x – 5y = -1
x – 3y = -3

1 solutions

Answer 386597 by sophxmai(60) About Me  on 2012-05-24 15:14:45 (Show Source):
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2x–5y=-1
x–3y=-3

You first want to get rid of one of the variables.
There are two different ways of doing this.
The first way is to solve the 2nd equation for x, and then plug it into the 1st equation to solve for y.
The second way is to multiply the 2nd equation by 2, and then subtract this new equation from the 1st equation so that x cancels out. Left with y, you solve for it.

The first way.
2x–5y=-1
x–3y=-3

Solve the 2nd equation for x
x-3y=-3
x=3y-3

Substitute x into the first equation
2x-5y=-1
2(3y-3)-5y=-1

Simplify and solve for y
2(3y-3)-5y=-1
6y-6-5y=-1
y=5

Plug y back into an equation with x in it.
x=3y-3
x=3(5)-3
x=15-3
x=12

The second way.
2x–5y=-1
x–3y=-3

Multiply the 2nd equation by 2
x–3y=-3
(x-3y=-3)x2
2x-6y=-6

Subtract the new equation from the first equation.
2x–5y=-1
2x-6y=-6
--------------
y=5

Plug y into an equation with x in it.
x–3y=-3
x-3(5)=-3
x-15=-3
x=12






Equations/614535: Find the choice below which gives a first step in solving the given system of equations by the addition method.
2x -3 y= 7
X-4y = 2
Do you; multiply the first equation by 3 and the second by 4
- multiply the first equation by -4 and the second by -2
-Multiply the second equation by 2
- Multiply the first equation by 4
1 solutions

Answer 386592 by sophxmai(60) About Me  on 2012-05-24 15:04:30 (Show Source):
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2x-3y=7
x-4y=2

The first step is to multiply the 2nd equation by 2.
This is because in order to solve it, you must cancel out one of the variables.
By multiplying the 2nd equation by 2, you can subtract the new equation (from multiplying the 2nd equation by 2) from the 1st equation, and get 0x. This leaves you with only y. You can then solve for y, and then plug y back into an equation with x and find x.

2x-3y=7
x-4y=2

Multiply the 2nd equation by 2
(x-4y=2)x2
2x-8y=4

Subtract this from the first equation
2x-3y=7
2x-8y=4
-------
5y=3

Solve for y
5y=3
y=3%2F5

Plug y back into an equation with x
x-4y=2
x-4%283%2F5%29=2
x-12%2F5=2
x=2%2B12%2F5
x=22%2F5


Miscellaneous_Word_Problems/609683: there are 340 tickets and three kids the mom wants to split them where james has 40 less than ashley and ashley gets 80 less than amanda how many tickets does each kid get
1 solutions

Answer 383898 by sophxmai(60) About Me  on 2012-05-10 18:33:24 (Show Source):
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Let:
x=James's tickets
y=Ashley's tickets
z=Amanda's tickets

Write your equations
x+y+z=340
x+40=y
y+80=z

Now solve your system...
x+40=y
x-y=-40

x+y+z= 340
x-y =-40
2y+z= 380
z= 380-2y

y+80=z
y+80=380-2y
y+2y=380-80
3y=300
y=100

z=380-2y
z=380-2(100)
z=380-200
z=180

x+40=y
x+40=100
x=60

Check:
x+y+z=340
60+100+180=340

James has 60 tickets.
Ashley has 100 tickets.
Amanda has 180 tickets.


Numbers_Word_Problems/609617: Find five consecutive even integers with a sum of -210
1 solutions

Answer 383888 by sophxmai(60) About Me  on 2012-05-10 18:18:22 (Show Source):
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(x)+(x+2)+(x+4)+(x+6)+(x+8)=-210
x+x+2+x+4+x+6+x+8=-210
5x+20=-210
5x=-230
x=-46

Check:
(-46)+(-44)+(-42)+(-40)+(-38)
=-46-44-42-40-38
=-90-120
=-210


Exponential-and-logarithmic-functions/609663: Solve 3%5E%288x%29=23
1 solutions

Answer 383886 by sophxmai(60) About Me  on 2012-05-10 18:13:48 (Show Source):
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Solve 3%5E%288x%29=23.

First, take the log of both sides
log%283%5E%288x%29%29=log%2823%29

Then move the exponent to the front of the log (it's a rule).
8xlog%283%29=log%2823%29

Now isolate the x.
8xlog%283%29=log%2823%29
8x=%28log%2823%29%29%2F%28log%283%29%29
x=%28log%2823%29%29%2F8%28log%283%29%29

That's the answer, unless you're allowed a calculator. If so, punch that into your calculator and you should get x=0.357


Age_Word_Problems/609678: Danny is twice as old as Kevin. Danny and Corey are the same age. Write an equation showing this.
1 solutions

Answer 383883 by sophxmai(60) About Me  on 2012-05-10 18:07:42 (Show Source):
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d=2k
d=c
c=2k
k=d/2
k=c/2


Rectangles/607684: The perimeter of a rectangle is 48 cm. The length is 6 cm less than twice the width. Which system would model this situation, and what are the length and the width?
1 solutions

Answer 382836 by sophxmai(60) About Me  on 2012-05-06 16:35:01 (Show Source):
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The perimeter of a rectangle is 48 cm. The length is 6 cm less than twice the width. Which system would model this situation, and what are the length and the width?

Let x=length and y=width
2x%2B2y=48
x%2B6=2y

Solve the 2nd equation for x or y (whichever is more convenient) and then plug into the 1st equation.
x%2B6=2y
x=2y-6

2x%2B2y=48
2%282y-6%29%2B2y=48
4y-12%2B2y=48
6y=60
y=10

Substitute y into a previous equation to solve for x.
x=2y-6
x=2%2810%29-6
x=20-6
x=14

The length is 14cm and the width is 10cm.


Geometry_Word_Problems/607666: The perimeter of a rectangular rose garden is 400 M. The length is 3 M more than twice the width. Find the length and width.
1 solutions

Answer 382830 by sophxmai(60) About Me  on 2012-05-06 16:27:52 (Show Source):
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The perimeter of a rectangular rose garden is 400 M. The length is 3 M more than twice the width. Find the length and width.

Let x=length, y=width
2x%2B2y=400
x-3=2y

Solve the 2nd equation for x or y, and then substitute it into the first equation.
x-3=2y
x=2y%2B3

2x%2B2y=400
2%282y%2B3%29%2B2y=400
4y%2B6%2B2y=400
6y=394
y=394%2F6
y=197%2F3

Now substitute y into a previous equation and solve for x.
x=2y%2B3
x=2%28197%2F3%29%2B3
x=394%2F3%2B3
x=403%2F3 or 134%281%2F3%29 depending how you want your answer


Expressions-with-variables/607676: how do you simplify 3 + x/2?
1 solutions

Answer 382819 by sophxmai(60) About Me  on 2012-05-06 16:13:34 (Show Source):
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Make it so that x is not a fraction
3%2Bx%2F2
=3%282%29%2B%28x%2F2%29%282%29
=6%2Bx


Miscellaneous_Word_Problems/607220:
1 solutions

Answer 382563 by sophxmai(60) About Me  on 2012-05-05 03:27:55 (Show Source):
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The length of a rectangle is 4 inches longer than twice its width. The area of the rectangle is 96 square inches. What is the length and width of the rectangle?

Let x=length and y=width
y-4=2x
xy=96

Solve the first equation for y and substitute it into the 2nd equation
y-4=2x
y=2x%2B4

xy=96
x%282x%2B4%29=96
2x%5E2%2B4x=96
2x%5E2%2B4x-96=0
2%28x%5E2%2B2x-48%29
2%28x%2B8%29%28x-6%29=0
x=-8%2C6
Reject x=-8 because the length cannot be a negative number
So x=6
Substitute x to find y
y=2x%2B4
y=2%286%29%2B4
y=12%2B4
y=16


Quadratic_Equations/607269: x^3+16x^2
1 solutions

Answer 382561 by sophxmai(60) About Me  on 2012-05-05 02:38:50 (Show Source):
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Factor out the x%5E2
x%5E3%2B16x%5E2
=x%5E2%28x%2B16%29

If it says to solve, equate it to 0 and solve for x
x%5E2%28x%2B16%29=0
x%5E2=0
x=0
and
x%2B16=0
x=-16


Numeric_Fractions/607279: can you show me how to divde 4 7/8 by 1/2?
1 solutions

Answer 382560 by sophxmai(60) About Me  on 2012-05-05 02:36:28 (Show Source):
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You want to divide 4 7/8 by 1/2

First make the 4 7/8 into an improper fraction
(4*8+7)/8=39/8

Now you have (39/8) divide by (1/2)
Flip the fraction after the divide sign and change the sign into a multiply sign

(39/8) x (2/1)

Now multiply them together
(39/8) x (2/1)
=(39/4)

If it says to make it into a proper fraction again, do so
39/4= 9 3/4


Surface-area/607280: the perimeter of a college athletic field is 92 meters and the length is 12 m more than the width. find the length and width.
1 solutions

Answer 382559 by sophxmai(60) About Me  on 2012-05-05 02:32:56 (Show Source):
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the perimeter of a college athletic field is 92 meters and the length is 12 m more than the width. find the length and width.
Let x=length and y=width
2x+2y=92
x-12=y

Substitute the 2nd equation into the first one
2x+2y=92
2x+2(x-12)=92
2x+2x-24=92
4x=116
x=116/4
x=29

Substitute x into one of the original equations
x-12=y
29-12=y
17=y

the length is 29m, the width is 17m


Age_Word_Problems/607031: The sum of the ages of a man and his wife is 80 years. 10 years ago, the ages of the wife was exactly two-third the age of the man. Find the present ages of the man and his wife.
1 solutions

Answer 382353 by sophxmai(60) About Me  on 2012-05-04 04:00:36 (Show Source):
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The sum of the ages of a man and his wife is 80 years. 10 years ago, the ages of the wife was exactly two-third the age of the man. Find the present ages of the man and his wife.

Let:
man's age = x
wife's age = y

x+y=80 <--sum of their age
y-10=2/3x <--10 years ago, the age of the woman was 2/3 of the man's current age

y=2/3x+10 <--solve the 2nd equation for y
x+2/3x+10=80 <--plug above into 1st equation
5/3x=70 <--simplify and solve
x=42 <--plug back into original equation to find y
42+y=80
y=80-42
y=38

Since x=42 and y=38
The man's age is 42 and the wife's age is 38


Permutations/607044:
1 solutions

Answer 382352 by sophxmai(60) About Me  on 2012-05-04 03:52:53 (Show Source):
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From a group of eight boys amd two girls a boy and a girl will be selected to attend a conference.
In how many ways can the selection be made?

First choose your boy:
8C1

Then choose your girl:
2C1

Now multiply them together
8C1 x 2C1
So now you get 8x2 which = 16


Age_Word_Problems/607061: please help me solve this problem.
Eva is 2 years older than Julienne. The sum of their ages is 20. Find their present ages.
1 solutions

Answer 382350 by sophxmai(60) About Me  on 2012-05-04 03:35:53 (Show Source):
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Eva is 2 years older than Julienne. The sum of their ages is 20. Find their present ages.

Let:
Eva's age = x
Julienne's age = y

x+y=20 <--the sum of their ages is 20
x-2=y <--Eva is 2 years older than Julienne

You can solve this system by either adding/subtracting or substituting.

Adding/Subtracting:
x+y=20
x-2=y

Rearrange the 2nd equation
x-2=y becomes x-y=2
So now we have

x+y=20
x-y=2
Now add the equations, you will get
2x=22
Now solve...
2x=22
x=11

Now that you have x, plug it into one of the equations to solve for y
x-y=2
11-y=2
11-2=y
9=y

Since x=11 and y=9
Eva's age is 11 and Julienne's age is 9
Substituting:
x+y=20
x-2=y

Since the 2nd equation is already arranged in a way that a variable = something... substitute it into the 1st equation.
x+y=20
x+(x-2)=20
x+x-2=20
2x-2=20
2x=22
x=11

Now that you have 11, plug x into your 2nd equation
x-2=y
11-2=y
9=y

Since x=11 and y=9
Eva's age is 11 and Julienne's age is 9


Equations/606860: Solve the system:
x^2+y^2=100
y-x=2
1 solutions

Answer 382293 by sophxmai(60) About Me  on 2012-05-03 18:38:04 (Show Source):
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Solve the system
x%5E2%2By%5E2=100
y-x=2

Solve the 2nd equation for y
y-x=2
y=x%2B2

So now you have
x%5E2%2By%5E2=100
y=x%2B2

Now substitute the 2nd equation into the 1st one
x%5E2%2B%28x%2B2%29%5E2=100

Now expand and group like terms
x%5E2%2B%28x%2B2%29%5E2=100
x%5E2%2Bx%5E2%2B4x%2B4=100
2x%5E2%2B4x-96=0

Now factor and solve
2x%5E2%2B4x-96=0
2%28x%5E2%2B2x-48%29=0
2%28x%2B8%29%28x-6%29=0

x%2B8=0 x-6=0
x=-8    x=6


Functions/379447: I need to evaluate the function at each specified value of the independent variable and simplify.
f(x) = the square root of (x+9) + 6 (the six is on the outside of the square root)
f(-9)
f(7)
f(x-9)
1 solutions

Answer 269381 by sophxmai(60) About Me  on 2010-12-01 22:22:41 (Show Source):
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f%28x%29=sqrt%28x%2B9%29%2B6
f(-9)=6
f(7)=10
f(x-9)=sqrt%28x%29%2B6

f%28x%29=sqrt%28x%2B9%29%2B6
f%28-9%29=sqrt%28x%2B9%29%2B6
f%28-9%29=sqrt%28%28-9%29%2B9%29%2B6
f%28-9%29=sqrt%280%29%2B6
f%28-9%29=6

f%28x%29=sqrt%28x%2B9%29%2B6
f%287%29=sqrt%28x%2B9%29%2B6
f%287%29=sqrt%287%2B9%29%2B6
f%287%29=sqrt%2816%29%2B6
f%287%29=4%2B6
f%287%29=10

f%28x-9%29=sqrt%28x%2B9%29%2B6
f%28x-9%29=sqrt%28x%2B9%29%2B6
f%28x-9%29=sqrt%28%28x-9%29%2B9%29%2B6
f%28x-9%29=sqrt%28x%29%2B6


Quadratic_Equations/379457: Wright a quadratic equation in the variable x having the given numbers as solutions. Type the equation in standard form, ax^2+bx+c=0
The solutions are -7,1

1 solutions

Answer 269379 by sophxmai(60) About Me  on 2010-12-01 22:16:42 (Show Source):
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x=-7, 1
0=(x+7)(x-1)
0=x%5E2-x%2B7x-7
0=x%5E2%2B6x-7


Graphs/379389: how do you put the two ponits (5,-5) (0,8) into slope intersept form
1 solutions

Answer 269363 by sophxmai(60) About Me  on 2010-12-01 21:19:50 (Show Source):
You can put this solution on YOUR website!
The points that are given to you are (5,-5) and (0,8).
The equation is y=mx+b.
What you need to find is the slope, m and the y-intercept, b.

To find the slope, m, you use the formula:
m=%28y2-y1%29%2F%28x2-x1%29
So, m=%28y2-y1%29%2F%28x2-x1%29
m=%288-%28-5%29%29%2F%280-5%29%29
m=%2813%29%2F%28-5%29

Now from y=mx+b, we have y=%28-13%2F5%29x%2Bb
To find the y-intercept, we can substitute one of the points in for x and y, and solve for b.

(0,8)
y=%28-3%2F5%29x%2Bb
%288%29=%28-13%2F5%29%280%29%2Bb
8=0%2Bb
8=b

Now from y=mx+b, we have y=%28-13%2F5%29x%2B8