Complex Rational Expressions

Muse Among Men

I am awful at math. So, so awful. I'm taking algebra 2 right now and floundering. We are working on complex rational expressions and I got the lesson the first day (yesterday), but today? Eehhh . . .The examples in the book aren't very helpful because they are just examples and don't tell you how to do it, and anything I've found online is dealing with very easy problems even I could do or are using a method different than what we were using.

For example: x^2 - y^2 divided by xy all over x-y divided by y. Now, I checked, and the answer is supposed to be x=y over y. What? I've done that same problem 3 or 4 times and still haven't gotten the correct answer.

Basically I am trying to get you guys to do my homework.

admanb

I'm not very good at math either, but that looks wrong to me. Here's my work:

(x^2-y^2)/xy / (x-y)/y
factor (x^2-y^2) into (x+y)(x-y), and multiply the numerator by the inverse of the denominator

= (x+y)(x-y)/xy * y/(x-y)
multiply

= (x+y)(x-y)y / xy(x-y)
cancel

= (x+y)/x

Muse Among Men

That made sense! Is there a guideline as to when to use the factoring method and when to use the lowest common denominator?

admanb

Fucked if I know. Try both and see which come out with the least messy answer. :P

(edit: wait, don't you only need the LCD for addition/subtraction?)