# How is this answer incorrect? partial fractions

• Dec 17th 2006, 05:14 PM
How is this answer incorrect? partial fractions
http://hosted.webwork.rochester.edu/...7b87455f91.png
I got that A=-x-5 and B=x^2-10 Apparently either one of them or both are wrong.
• Dec 17th 2006, 06:43 PM
AfterShock
Quote:

Originally Posted by badandy328
http://hosted.webwork.rochester.edu/...7b87455f91.png
I got that A=-x-5 and B=x^2-10 Apparently either one of them or both are wrong.

(4/(x - 4)) - (2/(x + 4)) = (2x + 24)/[(x - 4)*(x + 4)]

Note: x^2 - 16 = (x - 4)*(x + 4);

Thus, 2x + 24 + (-3x - 3) = -x + 21 (Which is your "A")

And then your B is the common denominator:

(x - 4)*(x + 4);

Thus, the final answer of A/B is:

(-x + 21)/[(x - 4)*(x + 4)]
• Dec 18th 2006, 08:20 AM
CaptainBlack
Quote:

Originally Posted by badandy328
http://hosted.webwork.rochester.edu/...7b87455f91.png
I got that A=-x-5 and B=x^2-10 Apparently either one of them or both are wrong.

What AfterShock said plus check the question, it is very unsual for a quadratic term to be written as $x^2+0x-16$.

RonL