Factor the equation x^2-3x-18

Question

asked Feb 10, 2019 31.0k views

1 Answer

ManiAm · Answer 1 · 2019-02-14T13:10:06+0000

This is a Non-Perfect Square Trinomial. To factor this type of trinomial, you have to remember this pattern:

(x+b)(x+b)=x^2+(a+b)x+ab

So you need to find two numbers
$a \ and \ b$ such that the product is
and the middle term is the sum
(a+b) . From our polynomial:

x^2-3x-18

Those numbers are:

$a=-6 \\ \\ b=3$

Because:

$ab=(-6)(3)=-18 \\ \\ a+b=-6+3=-3$

So:

$\boxed{x^2-3x-18=(x-6)(x+3)}$