# Subtracting polynomials

• Jul 9th 2013, 09:35 AM
Urpes
Subtracting polynomials
Just want to check what to do next, and any errors I made

Question: Add or subtract the following:

Having trouble typing equations in again so heres a quick pic
ImageShack® - Online Photo and Video Hosting

Then it says to list any restrictive values.

Are restrictive and undefined values different things?
• Jul 9th 2013, 11:01 AM
Soroban
Re: Subtracting polynomials
Hello, Urpes!

You made some errors . . .

Quote:

$\displaystyle \text{Simplify: }\;\frac{x+2}{(x-5)(x+2)} - \frac{2(x-7)}{(x-7)(x-5)}$

Note that:- $x \,\ne\, \text{-}2, 5, 7$

We have: . $\dfrac{x+2}{(x-5)(x+2)} - \dfrac{2(x-7)}{(x-7)(x-5)}$

Reduce: . $\dfrac{1}{x-5} - \frac{2}{x-5}$

Combine: . $\dfrac{1-2}{x-5} \;\;=\;\;\frac{-1}{x-5}$

Therefore: . $\dfrac{1}{5-x}$
• Jul 9th 2013, 12:12 PM
Urpes
Re: Subtracting polynomials
Ah I see, the only thing I don't get is the very last part? How did you get the denominator to be 5-x
• Jul 9th 2013, 12:21 PM
Shakarri
Re: Subtracting polynomials
Soroban multiplied the top and bottom by -1 to get the last line