# Subtracting polynomials

• Jul 9th 2013, 08:35 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
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Then it says to list any restrictive values.

Are restrictive and undefined values different things?
• Jul 9th 2013, 10:01 AM
Soroban
Re: Subtracting polynomials
Hello, Urpes!

You made some errors . . .

Quote:

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

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

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

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

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

Therefore: .$\displaystyle \dfrac{1}{5-x}$
• Jul 9th 2013, 11:12 AM
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, 11:21 AM
Shakarri
Re: Subtracting polynomials
Soroban multiplied the top and bottom by -1 to get the last line