# How do you factor y=x^2 + 3x -18 ?

Dec 15, 2015

Factor $y = {x}^{2} + 3 x - 18$

Ans: (x - 3)(x + 8)

#### Explanation:

Find 2 numbers knowing sum (+3 = b) and product (-18 = c). The 2 numbers have opposite signs.
Factor pairs of (-18)--> (-2, 9), (-3, 6). This sum is 3 = b. The 2 numbers are -3 and 6.
Factored form y = ( x - 3)( x + 6)