Originally Posted by

**pychon** I'm refreshing my math and a bit confused with the following expression and answer.

**Factoring:**

Solve: $\displaystyle (x+y)2+(x+y)b$

Answer: $\displaystyle (x+y)(2+b)$

or

Answer: $\displaystyle x+y(2+b)$

Solve: $\displaystyle 3(r-2s)-x(r-2s)$

Answer: $\displaystyle (r-2s)(3-x)$

or

Answer: $\displaystyle r-2s(3-x)$

If I were to try and check the answer given $\displaystyle (r-2s)(3-x)$... I've learned I need to distribute the problem to obtain the answer. In this case $\displaystyle r(3), r(-x), -2s(3), -2s(-x)$, which would give me a totally different answer of $\displaystyle 3r-rx-6s+2sx$, that is not an answer or how could one even derive $\displaystyle 3(r-2s)-x(r-2s)$.

If I were to check the answer with my solution $\displaystyle r-2s(3-x)$ ... $\displaystyle r-2s(3), r-2s(-x)$ ... I would then get $\displaystyle 3(r-2s)-x(r-2s) $

I'm lost...

Edit:

Going to basic math... mutliply/divide, add, subtract... anything in parenthesis is always solved first... so how can one justify using parenthesis in the first set of numbers in this answer!? "()" doesn't mean quantity... or does it...