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Bensky
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Integration with partial fractions -- help!
Here is the problem: http://img130.imageshack.us/img130/1673/integralthing.png
The answer should be 4.
N/A
Here are my steps so far:
(5x^2 - 17x + 10) / ((x-1)^3 * (x+1)) = A/(x-1) + B/(x-1)^2 + C/(x-1)^3 + D/(x+1)
5x^2 - 17x + 10 = A(x-1)^2(x+1) + B(x-1)(x+1) + C(x+1) + D(x-1)^3
Substituting 1 for x gives:
5-17+10 = 2C
C = -1
Substituting -1 for x gives:
5(-1)^2 - 17(-1) + 10 = -8D
D = -4
Variables C and D are correct according to the answer given to me on the practice test.
Now I'm at the point where I want to find the other 2 variables, A and B. I'm not sure how to go about doing this. I talked to my professor and she said something about plugging in random values for x and somehow getting A and B that way, but it didn't make much sense to me after she explained it. I have to be able to do this for a test where I will not be allowed anything but the Apple OSX calculator (it's basically the same as the Windows Calculator), so the easiest method to do this would be appreciated.
Thank you,
Bensky
Homework Statement
Here is the problem: http://img130.imageshack.us/img130/1673/integralthing.png
The answer should be 4.
Homework Equations
N/A
The Attempt at a Solution
Here are my steps so far:
(5x^2 - 17x + 10) / ((x-1)^3 * (x+1)) = A/(x-1) + B/(x-1)^2 + C/(x-1)^3 + D/(x+1)
5x^2 - 17x + 10 = A(x-1)^2(x+1) + B(x-1)(x+1) + C(x+1) + D(x-1)^3
Substituting 1 for x gives:
5-17+10 = 2C
C = -1
Substituting -1 for x gives:
5(-1)^2 - 17(-1) + 10 = -8D
D = -4
Variables C and D are correct according to the answer given to me on the practice test.
Now I'm at the point where I want to find the other 2 variables, A and B. I'm not sure how to go about doing this. I talked to my professor and she said something about plugging in random values for x and somehow getting A and B that way, but it didn't make much sense to me after she explained it. I have to be able to do this for a test where I will not be allowed anything but the Apple OSX calculator (it's basically the same as the Windows Calculator), so the easiest method to do this would be appreciated.
Thank you,
Bensky
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