How do you factor #2x²+15x-108#?
Comparing coefficients, we are looking for
I know that
Ultimately, it is always possible to use the general formula when solving quadratics like this, but spotting the factors of the constant term and trying a few possibilities will often get you the answer quicker.
There is another way that doesn't require guessing: the new AC Method to factor trinomials (Google, Yahoo Search)
Compose factor pairs of (a.c = -216). Proceed:....(-8, 27)(-9, 24). This last sum is 24 - 9 = 15 = b. Then, p' = -9 and q' = 24. Back to original
trinomial f(x) (1):