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Find the indefinite integral using integration by partial fractions: S 6/(x^3 -3x^2)...
Find the indefinite integral using integration by partial fractions: S 6/(x^3 -3x^2) dx
I find partial fractions difficult, but have possibly figured the following out:
but I'm not sure that is right, I have been unable to find any explenation on how to do a problem with 2 exponents in the denominator.
As always, any help would be greatly appreciated.
1 Answer | add yours
Best answer as selected by question asker.
You need to use partial fraction decomposition such that:
`6/(x^2(x-3)) = A/x + B/(x^2) + C/(x-3)`
Bringing the terms to the right to a common denominator yields:
`6 = A(x(x-3)) + B(x-3) + Cx^2`
`6 = Ax^2 - 3Ax + Bx - 3B + Cx^2`
`6 = x^2(A+C) + x(-3A + B) - 3B`
Equating the coefficients of like powers yields:
`A+C = 0 => A=-C`
`-3A+B = 0 => -3A = -B => 3A = B`
`-3B = 6 => B = -2 > A = B/3 => A = -2/3 => C = 2/3`
`6/(x^2(x-3)) = -2/(3x)- 2/(x^2) + 2/(3(x-3))`
Integrating both sides yields:
`int 6/(x^2(x-3)) dx= int -2/(3x) dx- int 2/(x^2) dx+ int 2/(3(x-3)) dx`
`int 6/(x^2(x-3)) dx = -(2/3)ln|x| - 2 int x^(-2)dx + (2/3)ln|x-3| `
`int 6/(x^2(x-3)) dx = -(2/3)ln|x| + 2/x + (2/3)ln|x-3| + c`
`int 6/(x^2(x-3)) dx = (2/3)ln|(x-3)/x| + 2/x + c`
Hence, evaluating the indefinite integral using partial fraction decomposition, yields `int 6/(x^2(x-3)) dx = (2/3)ln|(x-3)/x| + 2/x + c.`
Posted by sciencesolve on November 7, 2012 at 6:26 PM (Answer #1)
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