#### Answer

(x+9)(x-10)

#### Work Step by Step

$x^{2}$ - x -90
step 1. Enter x as the first term of each factor
$x^{2}$ - x - 90= (x__)(x _)
Step 2. To find the second term of each factor, we must find two integers whose product is -90 and whose sum is -1
List pairs of factors of the constant, -90
(1,-90)(-1,90)(-2,45)(2,-45)(3,-30)(-3,30)(5,-18)(-5,18)(6,-15)(-6,15)(9,-10)(-9,10)
step 3. The correct factorization of $x^{2}$ - x - 90 is the one in which the sum of the Outside and Inside products is equal to -x.
So (9,-10) satisfy the condition
$x^{2}$ -x -90 = $x^{2}$ +9x -10x - 90= (x+9)(x-10)