# partial fractions

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• Sep 12th 2009, 02:45 PM
helloworld101
partial fractions
hi all

am getting trouble expressing the following as a partial fraction. Can u assit me in solving it please.

5x - x^2
____________
x(x-1)(2x+1)
• Sep 12th 2009, 02:56 PM
pickslides
Consider this

$\displaystyle \frac{5x-x^2}{x(x-1)(x-2)} =\frac{A}{x} +\frac{B}{x-1} +\frac{C}{x-2}$

$\displaystyle 5x-x^2 =A(x-1)(x-2) +B(x-2)x +C(x-1)x$

now choose values for x to solve for $\displaystyle A,B$ and $\displaystyle C$.

(Rock)
• Sep 12th 2009, 03:08 PM
helloworld101
how did u get (x-2)
• Sep 12th 2009, 03:16 PM
mr fantastic
Quote:

Originally Posted by helloworld101
how did u get (x-2)

It was a typo but the suggestion on what to do is still completely valid (all you have to do is make the required trivial correction and then continue).
• Sep 12th 2009, 03:16 PM
pickslides
Oops!

Must have had $\displaystyle x-2$ on the mind. Just use my first post and replace $\displaystyle x-2$ with $\displaystyle 2x+1$ and you'll be back on track.

Does that help?
• Sep 12th 2009, 03:35 PM
helloworld101
thanks got the answer in the back of the book now...