The only factoring you need to do is already done for you:
x² + x - 12 = (x + 4) (x - 3)
What you're asked to do is decompose
(3x - 4) / (x² + x - 12)
into partial fractions, i.e. find a and b such that
(3x - 4) / (x² + x - 12) = a / (x + 4) + b / (x - 3)
Multiply both sides by x² + x - 12 :
3x - 4 = a (x - 3) + b (x + 4)
3x - 4 = (a + b) x + (-3a + 4b)
So we have
a + b = 3
-3a + 4b = -4
and solving this system gives
a = 16/7 and b = 5/7
so you should submit the numbers in bold:
(3x - 4) / (x² + x - 12) = 16 / (7 (x + 4)) + 5 / (7 (x - 3))
