Sarah Jane T. answered 09/07/12
Enthusiastic, experienced math tutor!
2x/(x-3) + (4x-6)/(x2-9)
The first thing you want to do is factor the denominator in the second expression. x2-9 is can be factored to (x-3)(x+3) -- this is a special factoring case, the difference of squares, that you should learn to recognize because you'll be using it a lot! (a+b)(a-b) = a2-b2.
2x/(x-3) + (4x-6)/((x+3)(x-3))
Now you need a common denominator so you can add the two fractions. (x+3)(x-3) will be the common denominator. The first expression should be multiplied by (x+3)/(x+3); the second expression already has the correct denominator.
(2x(x+3))/((x+3)(x-3)) + (4x-6)/((x+3)(x-3))
Now, since the fractions have a common denominator, you can add the numerators.
(2x(x+3) + (4x-6)) / ((x+3)(x-3))
Next, distribute the 2x to the x+3.
(2x2+6x+4x-6) / ((x+3)(x-3))
Combine like terms in the numerator.
(2x2+10x-6) / ((x+3)(x-3))
Factor a 2 out of the numerator.
2(x2+5x-3) / ((x+3)(x-3))
You can't factor x2+5x-3, so this is your final answer. Often, in problems like this, you would be able to factor the numerator and one of the factors would end up canceling with the denominator.