# Thread: Rational Expressions help!

1. ## Rational Expressions help!

how to solve for this one

1)2x+y/x-y - 3x-y/x+y

2)x+3/2x^2-15x+18 + x-1/2x^2-13x+15

ty in advance.

2. To add the expressions, try to get both expressions to have the same denominator. For instance, if I want to combine the following expressions:
$\frac{1}{x+2} + \frac{2}{x^2-4}$

I can make them have the same denominator if I look more closely:
$\frac{1}{x+2} + \frac{2}{(x+2)(x-2)}$

So, what I need to do to make them have the same denominator is simply to multiply the $x-2$ with the numerator and denominator of the first expression.
$\frac{1 \cdot (x-2)}{(x+2) \cdot (x-2)} + \frac{2}{(x+2)(x-2)}$