(x+1)(x-2)=18

Solution for (x+1)(x-2)=18 equation:

Simplifying
(x + 1)(x + -2) = 18

Reorder the terms:
(1 + x)(x + -2) = 18

Reorder the terms:
(1 + x)(-2 + x) = 18

Multiply (1 + x) * (-2 + x)
(1(-2 + x) + x(-2 + x)) = 18
((-2 * 1 + x * 1) + x(-2 + x)) = 18
((-2 + 1x) + x(-2 + x)) = 18
(-2 + 1x + (-2 * x + x * x)) = 18
(-2 + 1x + (-2x + x2)) = 18

Combine like terms: 1x + -2x = -1x
(-2 + -1x + x2) = 18

Solving
-2 + -1x + x2 = 18

Solving for variable 'x'.

Reorder the terms:
-2 + -18 + -1x + x2 = 18 + -18

Combine like terms: -2 + -18 = -20
-20 + -1x + x2 = 18 + -18

Combine like terms: 18 + -18 = 0
-20 + -1x + x2 = 0

Factor a trinomial.
(-4 + -1x)(5 + -1x) = 0

Subproblem 1
Set the factor '(-4 + -1x)' equal to zero and attempt to solve:

Simplifying
-4 + -1x = 0

Solving
-4 + -1x = 0

Move all terms containing x to the left, all other terms to the right.

Add '4' to each side of the equation.
-4 + 4 + -1x = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -1x = 0 + 4
-1x = 0 + 4

Combine like terms: 0 + 4 = 4
-1x = 4

Divide each side by '-1'.
x = -4

Simplifying
x = -4
Subproblem 2
Set the factor '(5 + -1x)' equal to zero and attempt to solve:

Simplifying
5 + -1x = 0

Solving
5 + -1x = 0

Move all terms containing x to the left, all other terms to the right.

Add '-5' to each side of the equation.
5 + -5 + -1x = 0 + -5

Combine like terms: 5 + -5 = 0
0 + -1x = 0 + -5
-1x = 0 + -5

Combine like terms: 0 + -5 = -5
-1x = -5

Divide each side by '-1'.
x = 5

Simplifying
x = 5
Solution
x = {-4, 5}