SOLUTION: I am trying to simplify 2 fraction problems with variables and exponents, probably using factoring, but depite all the factoring I have tried, my answers don't come up with common

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Question 162413: I am trying to simplify 2 fraction problems with variables and exponents, probably using factoring, but depite all the factoring I have tried, my answers don't come up with common denominators, so the numbers don't combine. Here is the first problem:
yx^2/(x-y)+xy^3/(xy-x^2)

This is the second:
1/(a^2+b^2)+1/(a^2-b^2)+2b^2/(a^4-b^4)
Any help you can give would be REALLY awesome!

Found 2 solutions by stanbon, jim_thompson5910:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Here is the first problem:
yx^2/(x-y)+xy^3/(xy-x^2)
= yx^2/(x-y)+xy^3/(-x(x-y))
The LCD = -x(x-y)
= -yx^3/lcd + xy^3/lcd
= [-yx^3 + xy^3]/lcd
= [-xy(x^2 - y^2)]/[-x(x-y)]
= [y(x + y)]
==============================

This is the second:
1/(a^2+b^2) + 1/(a^2-b^2) + 2b^2/(a^4-b^4)
lcd = a^4 - b^4
-----------------------
= (a^2 - b^2)/lcd + (a^2 + b^2)/lcd + 2b^2/lcd
Add the three numerators to get:
= (2a^2 + 2b^2)/lcd
= [2(a^2+b^2)] / [(a^2+b^2)(a^2-b^2)]
= 2/(a^2-b^2)
==========================================
Chers,
Stan H.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
I'll do the first one to get you started

%28yx%5E2%29%2F%28x-y%29%2B%28xy%5E3%29%2F%28xy-x%5E2%29+ Start with the given expression


%28yx%5E2%29%2F%28x-y%29%2B%28xy%5E3%29%2F%28-x%28x-y%29%29+ Factor the second denominator


%28yx%5E2%29%2F%28x-y%29-%28xy%5E3%29%2F%28x%28x-y%29%29+ Simplify


So we can see that the LCD is x%28x-y%29. So we need to multiply the first fraction by x%2Fx to get the denominator to the LCD


%28x%2Fx%29%28%28yx%5E2%29%2F%28x-y%29%29-%28xy%5E3%29%2F%28x%28x-y%29%29+ Multiply the first fraction by x%2Fx


%28x%28yx%5E2%29%29%2F%28x%28x-y%29%29-%28xy%5E3%29%2F%28x%28x-y%29%29+ Combine the fractions


%28x%5E3y%29%2F%28x%28x-y%29%29-%28xy%5E3%29%2F%28x%28x-y%29%29+ Multiply


%28x%5E3y-xy%5E3%29%2F%28x%28x-y%29%29 Combine the fractions


So %28yx%5E2%29%2F%28x-y%29%2B%28xy%5E3%29%2F%28xy-x%5E2%29+ simplifies to %28x%5E3y-xy%5E3%29%2F%28x%28x-y%29%29