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drk answered: 1901 problems
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Graphs/263441: how do you graph the equation y = -8/5 using the slope and y-intercept method?
1 solutions

Answer 194137 by drk(1908) About Me  on 2010-01-31 14:29:49 (Show Source):
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Normally we want
y+=+mx+%2B+b
where m = slope and b = y-intercept.
in our example we have
y+=+-8%2F5
which means
y+=+0x+-+8%2F5
or m = 0 and b = -8/5.
to graph
first plot -8/5 on the y-axis.
second move up 0 and over 1 (rise / run) and place a dot.
connect the dots to find a long horizontal line.


Evaluation_Word_Problems/263438: Given G(t) = 4 − 7t, write G( 5 + h) − G(5) in simplest form.
1 solutions

Answer 194132 by drk(1908) About Me  on 2010-01-31 14:26:33 (Show Source):
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the problem is
Given G(t) = 4 − 7t, write G(5 + h) − G(5) in simplest form.
step 1 - replace t with 5+h to get
G(5+h) = 4 - 7(5+h)
distribute to get
G(5+h) = 4 - 35 -7h
combine like terms to get
G(5+h) = -7h - 31
---
G(5) = 4 - 7*5 = 4 - 35 = -31
---
G(5+h) - G(5) = -7h - 31 - (-31) = -7h


Evaluation_Word_Problems/263440: The sum of two numbers is 39. The greater number is 5 less than 3 times the smaller number. What are the two numbers?
1 solutions

Answer 194131 by drk(1908) About Me  on 2010-01-31 14:23:47 (Show Source):
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We
(i) a + b = 35
(ii) a = 3b - 5
substituting (ii) into (i), we get
(iii) 3b-5 + b = 35
combine like terms to get
(iv) 4b - 5 = 35
adding 5 we get
(v) 4b = 40
dividing, we get
b = 10
so
a = 25


Mixture_Word_Problems/263434: A silversmith mixed 30 g of a 70% silver alloy with 50 g of a 15% silver alloy. What is the percent concentration of the resulting alloy? (Round your answer to the nearest tenth of a percent.)
1 solutions

Answer 194129 by drk(1908) About Me  on 2010-01-31 14:21:43 (Show Source):
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This is a mixture problem with out mixture information. Here is a table based on the given information
alloy . . . . . .% . . . . . .g . . . . . . .%g
70 . . . . . . . 70 . . . . 30 . . . . . .2100
15 . . . . . . .15 . . . . .50 . . . . . .750
mix . . . . . . x . . . . . .80 . . . . . .80x
looking at the third column, we get
2100+%2B+750+=+80x
adding we get
2850+=+80x
dividing, we get
x = 35.625
which is
35.63% = 35.6%


Age_Word_Problems/263432: In 1992 the life expectancy of males in a certain country was 66.2 years in 1997 it was 69.9 years let E represent the life expectancy in year t and let t represent the number of years since 1992?
1 solutions

Answer 194127 by drk(1908) About Me  on 2010-01-31 14:16:48 (Show Source):
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I think you are looking for a linear equation to model this data. We have two coordinates here
(0, 66.2) and (5, 69.9). Let 1992 = 0 and 1997 = 5.
step 1 - find the slope using
m+=+%28y2-y1%29%2F%28x2-x1%29
to get
m+=+%2869.9-66.2%29%2F%285-0%29
which is
m+=+3.7%2F5
---
step 2 - using y = mx + b, and a coordinate, we get
y+=+mx+%2B+b
66.2+=+%283.7%2F5%29%2A0+%2B+b
so,
b=66.2
---
we have our answer as
y+=+%283.7%2F5%29x+%2B+66.2


Linear-systems/263429: Determine whether the system is consistent, inconsistent, or dependent.
3x - 3y = -9
9x - 9y = -27
Determine whether the system is consistent, inconsistent, or dependent.
2x + 2y = 2
6x + 6y = 6
1 solutions

Answer 194125 by drk(1908) About Me  on 2010-01-31 14:12:57 (Show Source):
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Lets take these one at a time:
Determine whether the system is consistent, inconsistent, or dependent.
(i) 3x+-+3y+=+-9
(ii) 9x+-+9y+=+-27
step 1 - multiply (i) by -3 to get
(iii) -9x+%2B+9y+=+27
step 2 - add (ii) and (iii) to get
(iv) 0+%2B+0+%2B+0
Here we have dependent , consistent
Determine whether the system is consistent, inconsistent, or dependent.
(i) 2x+%2B+2y+=+2
(ii) 6x+%2B+6y+=+6
step 1 - multiply (i) by -3 to get
(iii) -6x+-6y+=+-6
step 2 - add (ii) and (iii) to get
(iv) 0+%2B+0+%2B+0
Here we have dependent , consistent


Mixture_Word_Problems/263426: A butcher has some hamburger that is 29% fat and some that is 15% fat. How many pounds of each should be mixed to make 63 lb of hamburger that is 17% fat?
1 solutions

Answer 194124 by drk(1908) About Me  on 2010-01-31 14:07:35 (Show Source):
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This is a mixture problem. Here is a table based on the given information
fat . . . . . . .% . . . . . . pounds . . . . . . . . %-pounds
29. . . . . . . 29 . . . . . . . .p . . . . . . . . . . .29p
15 . . . . . . .15 . . . . . . . .63-p. . . . . . . . .945 -15p
17 . . . . . . .17 . . . . . . . .63. . . . . . . . . . .1071
set the third column equal to get
29p+%2B+945+-+15p+=+1071
combine like terms to get
14p+%2B+945+=+1071
subtract 945 to get
14p+=+126
p = 9 pounds @ 29 %
63-p = 54 pounds @ 15%


Mixture_Word_Problems/263420: A ferry leaves a harbor and travels to a resort island at an average speed of 22 mph. On the return trip, the ferry travels at an average speed of 10 mph because of fog. The total time for the trip is 4 h. How far is the island from the harbor?
1 solutions

Answer 194122 by drk(1908) About Me  on 2010-01-31 14:01:23 (Show Source):
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This is an RTD problem. Here is a table based on the given information
location . . . . . rate . . . . .time . . . . . distance
resort . . . . . . . .22 . . . . .t. . . . . . . . . . 22t
harbor . . . . . . .10 . . . . .4-t. . . . . . . . . 40-10t
total. . . . . . . . . . . . . . . . 4
since distances are =, set
22t+=+40-10t
add 10t to get
32t+=+40
divide by 32 to get
t+=+1.25 hours
we want distance, so
22*1.25 = 27.5 miles


Travel_Word_Problems/263413: Henry can ride his horse at 4 miles per hour and get to the battlefield on time. If he stops for 1 hour to make a speech to his troups, he must ride 5 miles per hour for the whole trip to get to the battlefield on time. How far is it to the battlefield?
1 solutions

Answer 194119 by drk(1908) About Me  on 2010-01-31 13:56:55 (Show Source):
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This is an RTD problem. Here is a table based on the given information
travel . . . . . rate . . . . . .time . . . . . .distance
horse . . . . . . 4 . . . . . . . .t . . . . . . . . .4t
speech . . . . . 5 . . . . . . . t-1 . . . . . . . 5t - 5
set
4t+=+5t+-+5
subtract 5t to get
-t+=+-5
so
t = 5.
distance = 4t = 20 miles


Polynomials-and-rational-expressions/263411: Factor the expression on the left side of each equation. Then solve the equation
4x³-32=0
1 solutions

Answer 194116 by drk(1908) About Me  on 2010-01-31 13:30:49 (Show Source):
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The original equation was
4x%5E3-32=0
step 1 - rewrite the left side as
%284%5E%281%2F3%29%5E3%29%2Ax%5E3+-+%282%5E%285%2F3%29%29%5E3+=+0
and then using difference of cubes, we get

set each part = 0 and solve to get
%284%5E%281%2F3%29%2Ax+-+2%5E%285%2F3%29%29+=+0
add 2^(5/3) to get
4%5E%281%2F3%29%2Ax+=+2%5E%285%2F3%29
divide by 4^(1/3) to get
x+=+2
the other parentheses, trinomial, will generate imaginary answers. so we get
x = 2.


Rate-of-work-word-problems/263393: An 8 hp pump can fill a tank in 8 hours. A smaller 3 hp pump fills the same tank in 12 hours. The pumps are used together to begin filling this tank. After four hours, the 8 hp pump breaks down. How long will it take the smaller pump to fill the tank?
1 solutions

Answer 194114 by drk(1908) About Me  on 2010-01-31 13:20:30 (Show Source):
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This is a working together problem.
The rate of the 8 hp pump = 1/8
the rate of the 3 hp pump is 1/12
The time together will be 4 hours.
The time that the 3 hp pump works alone is x hrs.
We want to fill only 1 tank
-----
we use the formula
%281%2F8%29%2A4+%2B+%281%2F12%29%2A4+%2B+%281%2F12%29%2Ax+=+1
we get
4%2F8+%2B+4%2F12+%2B+x%2F12+=+1
adding the fractions, we get
+5%2F6+%2B+x%2F12+=+1
subtract 5/6 to get
x%2F12+=+1%2F6
multiply by 12 to get
x+=+2
So, the 3 hp pump must work and additional 2 hours.


Quadratic-relations-and-conic-sections/263410: How do you tell which way a parabola will open by their equation?
1 solutions

Answer 194110 by drk(1908) About Me  on 2010-01-31 13:16:10 (Show Source):
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The general parabola formula is
y+=+ax%5E2+%2B+bx+%2B+c
or
y+=+a%28x-h%29%5E2+%2B+k
in either case to determine up or down, look at the "a" value
If "a' is positive, then it opens up
if "a" is negative, then it opens down


Rectangles/263394: What is the perimeter and area of the rectangle that is 33 m wide and 2 m long?
1 solutions

Answer 194109 by drk(1908) About Me  on 2010-01-31 13:14:20 (Show Source):
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Perimeter formula is
P+=+2L+%2B+2W
area formula is
A+=+LW
---
from the given information, we get
P+=+2%2A33%2B+2%2A2}
P+=+66+%2B+4
P = 70 m
---
from the given information, we get
A+=+33%2A2
A = 66 meters squared.


Miscellaneous_Word_Problems/263404: If the patterns of the fines continue at the same rate of increase at what speed will the fines be the same? Given: County A rate is +15, County B rate is +10; at 60mph fine for County A is $0 and the fine for County B is $40.
1 solutions

Answer 194107 by drk(1908) About Me  on 2010-01-31 13:11:30 (Show Source):
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If I understand the question correctly, we have two equations
(i) 15%28m-60%29
(ii) 10%28m-60%29%2B40
setting them equal, we get
15%28m-60%29+=+10%28m-60%29%2B40
distribute to get
15m+-+900+=+10m+-+600+%2B+40
combine like terms to get
15m+-+900+=+10m+-+560
subtract 10m and add 900 to get
5m+=+340
divide to get
m+=+68
So, at 68 mph,
city A fine will be $120
city B fine will be $120


Polynomials-and-rational-expressions/263409: 2x³-250=0
1 solutions

Answer 194104 by drk(1908) About Me  on 2010-01-31 13:03:41 (Show Source):
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Here is the given equation
2x%5E2-250=0
step 1 - add 250 to get
2x%5E3++=+250
step 2 - divide by 2 to get
x%5E3+=+125
step 3 - take a cube root of both sides to get
x+=+5


Linear-equations/263407: Solve the following system of linear equations. If possible, express your answer as an ordered pair (x,y). Also, tell whether the system of equations is “independent”, “inconsistent”, or “dependent”.
2x-4y=8
x-2y=4

1 solutions

Answer 194103 by drk(1908) About Me  on 2010-01-31 13:02:09 (Show Source):
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Here is our original system
(i) 2x-4y=8
(ii) 1x-2y=4
step 1 - multiply (ii) by -2 to get
(iii) -2x+%2B+4y+=+-8
add (ii) and (iii) to get
(iv) 0+%2B+0+=+0
this mans that we have the same equations but in disguise.
These equations are "dependent"


Polynomials-and-rational-expressions/263408: X³+64=0
1 solutions

Answer 194102 by drk(1908) About Me  on 2010-01-31 12:59:46 (Show Source):
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here is the given equation
X%5E3%2B64=0
step 1 - subtract 64 to get
x%5E3+=+-64
step 2 - take a cube root of both sides to get
x+=+-4
this is the only "real" solution.
There are 2 imaginary solutions.


Permutations/263406: How many six-letter permutations can be formed from the first nine letters of the alphabet?
1 solutions

Answer 194101 by drk(1908) About Me  on 2010-01-31 12:58:01 (Show Source):
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We use the permutation formula:
nPr and get
9P6 = 60,480


Reduction-of-unit-multipliers/263405: Name the period of the first three digits: 234,837,925.00
1 solutions

Answer 194100 by drk(1908) About Me  on 2010-01-31 12:56:50 (Show Source):
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The 234 occur in the millions period.


Number-Line/263397: cant seem to solve this one.. i have to put it on a number line too
x^2 + 2x > 3
Thanks!
1 solutions

Answer 194099 by drk(1908) About Me  on 2010-01-31 12:55:55 (Show Source):
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here is the original question
x%5E2+%2B+2x+%3E+3
step 1 - subtract 3 to get
x%5E2%2B2x+-+3+%3E+0
step 2 -factor to get
%28x%2B3%29%28x-1%29+%3E+0
step 3 we need to create 3 number line graphs. Make sure the 0 marker is aligned in all three.
number line graph #1:
x+3> 0
this means open circle above -3 and then + signs to the right and - signs to the left.
number line graph #2:
x-1> 0
this means open circle above +1 and then + signs to the right and - signs to the left.
number line graph #3:
(x+3)(x-1) > 0
we place open circles above -3 and then +1.
To the left of -3, we have - signs for both lines. - x - = + so in the third number line place a + to the left of -3.
Between -3 and +1 we have different signs, so place a - sign on the third number line between -3 and +1.
To the right of +1, we have + signs for both lines. + x + = +, so in the third number line place a + to the right of +1.
we want where the signs are > 0 or the + regions.
Our final answer is
open circles above -3 and +1 and then arrow from the -3 to the left and arrow from the +1 to the right.


Travel_Word_Problems/263398: A cylindrical drum has a diameter of 3 yards and a volume of 65 cubic yards. What is the height of the drum? (Hint: Use V = пr2h)
1 solutions

Answer 194098 by drk(1908) About Me  on 2010-01-31 12:46:11 (Show Source):
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Using our volume formula as
V+=+pi%2Ar%5E2%2Ah
and our given information, we get
65+=+pi%2A1.5%5E2%2Ah
notice I didn't use 3. D = 3, so r = 1.5
65+=+2.25%2Api%2Ah
by division, we get
h+=+9.1956 yrds


Triangles/263396: Two sides of a triangle have the same length. The third side measures 4 m less than twice that length. The perimeter of the traiangle is 24 m. Find the lengths of the 3 sides.
1 solutions

Answer 194097 by drk(1908) About Me  on 2010-01-31 12:43:13 (Show Source):
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Let x be the length of each equal side and then 2x - 4 is the length of the base.
p = a + b + c
24 = a + b + c
24+=+x+%2B+x+%2B+2x+-+4
step 1 - combine like terms to get
24+=+4x+-+4
step 2 - add 4 to get
28+=+4x
step 3 - divide by 4 to get
x+=+7
the three sides are
{7, 7, 10}


Number-Line/263392: please help me solve this equation...
+1%2F%28x%2B1%29+%2B+1%2F%28x%2B2%29+%3C+0+
1 solutions

Answer 194096 by drk(1908) About Me  on 2010-01-31 12:40:36 (Show Source):
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here is the original equation
+1%2F%28x%2B1%29+%2B+1%2F%28x%2B2%29+%3C+0+
step 1 - multiply by the common denominator of (x+1)(x+2) to get
x%2B2+%2B+x%2B1+%3C+0
step 2 - combine like terms to get
2x+%2B+3+%3C+0
step 3 - subtract 3 to get
2x+%3C+-3
step 4 - divide to get
x+%3C+%28-3%2F2%29


Mixture_Word_Problems/263387: What values are excluded from the domain of the function? (Separate multiple answers with commas. Enter NONE if there are none.)
F(x) = (3 x - 9)/(x - 8)
1 solutions

Answer 194093 by drk(1908) About Me  on 2010-01-31 12:31:45 (Show Source):
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To determine the domain of any function, we ask 2 questions
(1) is the variable in a square root of any type?
if "yes" set the stuff under the root >= 0 and solve for x.
if "no" go to question 2.
(2) is the variable information in the denominator?
if "yes" set the denominator stuff not = 0 and solve for x.
if "no" then you say "all reals"
-----
Using these questions on the given problem., we get
(1) NO
(2) YES
so
x-8+=+0
solving for x, we get
x = 8.
This means we cannot use x = 8 as a domain number.


Quadratic_Equations/263376: can any quadratic function of the form y=ax^2+bx+c be changed into a quadratic function in vertex form by completing a square?
1 solutions

Answer 194092 by drk(1908) About Me  on 2010-01-31 12:26:59 (Show Source):
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The answer is yes. By completing the square you convert the quadratic equation into the vertex form of a parabola. After the process is done you end up with the following:
y+=+a%28x-%28b%2F%282a%29%29%29%5E2+%2B+%284ac-b%5E2%29%2F%282a%29


Square-cubic-other-roots/263378: Verify that -2 is a root of the equation 2x%5E3%2Bx%5E2-10x-8=0
Find the other two roots, correct to 2 decimal places.
1 solutions

Answer 194089 by drk(1908) About Me  on 2010-01-31 12:20:15 (Show Source):
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we can use synthetic division to verify. This will generate another equation that we will factor.
-2 // . . . 2 . . . . 1 . . . . -10 . . . . . -8
. . . . . . . . . . . . -4 . . . . .6 . . . . . . .8
. . . . . . . 2 . . . . -3 . . . . -4 . . . // . 0
So, we have verified by getting a 0 remainder. We now have a new equation of the form
2x%5E2+-+3x+-+4+=+0
By quadratic, we get
x+=+%283+%2B-+sqrt%289-4%2A2%2A%28-4%29%29%29%2F%284%29
and then
x+=+%283+%2B-+sqrt%2841%29%29%2F%284%29
we have two answers and rounded, we get
x ~ 2.35
x ~ -0.85


Number-Line/263375: (1/x)/(x-3) can you break this down for me step by step? Thanks
1 solutions

Answer 194088 by drk(1908) About Me  on 2010-01-31 12:15:10 (Show Source):
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here is the original problem
%281%2Fx%29/%28x-3%29
step 1 - multiply by 1/(x-3) to get
%281%2Fx%29%2A%281%2F%28x-3%29%29/%28x-3%29%2A%281%2F%28x-3%29%29
notice the denominator x-3 parts drop out, so we get
%281%2Fx%29%2A%281%2F%28x-3%29%29
which is
1%2F%28x%2A%28x-3%29%29


real-numbers/263369: Cant seem to figure this one out :/
Find all solutions of the equation and express them in the form (a+bi)
2x^2 - 2x + 3 = 0
1 solutions

Answer 194086 by drk(1908) About Me  on 2010-01-31 12:12:06 (Show Source):
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here is the original equation
2x%5E2+-+2x+%2B+3+=+0
step 1 - using quadratic, we get
x+=+%282+%2B-+sqrt%284-4%2A2%2A3%29%29%2F%284%29
and then
x+=+%282+%2B-+sqrt%28-20%29%29%2F%284%29
simplifying the radical, we get
x+=+%282+%2B-+2isqrt%285%29%29%2F%284%29
and canceling, we get
x+=+%281+%2B-+isqrt%285%29%29%2F%282%29


Functions/263371: 5/x+3 - 1/x = 1/2
1 solutions

Answer 194085 by drk(1908) About Me  on 2010-01-31 12:09:43 (Show Source):
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here is the original equation
5%2Fx%2B3+-+1%2Fx+=+1%2F2
step 1 - multiply by 2x to get
10+%2B+6x+-+2+=+x
step 2 - subtract x and subtract 8 to get
5x+=+-8
by division, we get
x+=+-8%2F5


real-numbers/263370: Find all solutions of the equation and express them in the form (a+bi)
z + 4 + 12/z = 0
Thanks :)
1 solutions

Answer 194083 by drk(1908) About Me  on 2010-01-31 12:07:18 (Show Source):
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here is our original equation:
z+%2B+4+%2B+12%2Fz+=+0+
step 1 - multiply by z to get
z%5E2+%2B+4z+%2B+12+=+0
using the quadratic, we get
x+=+%28-4+%2B-+sqrt%2816-4%2A1%2A12%29%29%2F%282%29
which becomes
x+=+%28-4+%2B-+sqrt%28-32%29%29%2F%282%29
and then
x+=+%28-4+%2B-+4isqrt%282%29%29%2F%282%29
canceling, we get
x+=+-2+%2B-+2isqrt%282%29


logarithm/263191: Evaluate the expression:
e^In(x+1)^2
1 solutions

Answer 193953 by drk(1908) About Me  on 2010-01-30 20:03:20 (Show Source):
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e%5EIn%28x%2B1%29%5E2
the e and ln drop out and we are left with
%28x%2B1%29%5E2