How do you factor the expressions x^2+7x-18?

3 Answers
May 12, 2018

(x+9)(x-2)

Explanation:

Given: x^2+7x-18.

Split the middle term.

=>x^2+9x-2x-18.

Factor by each side.

=>x(x+9)-2(x+9).

=>(x+9)(x-2)

May 12, 2018

(x+9)(x-2)

Explanation:

"since the coefficient of the "x^2" term is 1 then"

"the factors of - 18 which sum to + 7 are + 9 and - 2"

rArrx^2+7x-18=(x+9)(x-2)

May 12, 2018

(x+9)(x-2)

Explanation:

With this type of quadratic, we need to find a number that adds to make 7, but multiplies to make -18:

We can start by listing the factors of 18:

-18 and 1

-1 and 18

-9 and 2

-2 and 9

-6 and 3

-3 and 6

9+(-2)=7 lArr "therefore this combination will work"

Place in double brackets:

(x+9)(x-2)

We can check by expanding:

(x+9)(x-2)=x^2-2x+9x-18

rArr x^2+7x-18