(x+6)(2x-6)=720

Solution for (x+6)(2x-6)=720 equation:

Simplifying
(x + 6)(2x + -6) = 720

Reorder the terms:
(6 + x)(2x + -6) = 720

Reorder the terms:
(6 + x)(-6 + 2x) = 720

Multiply (6 + x) * (-6 + 2x)
(6(-6 + 2x) + x(-6 + 2x)) = 720
((-6 * 6 + 2x * 6) + x(-6 + 2x)) = 720
((-36 + 12x) + x(-6 + 2x)) = 720
(-36 + 12x + (-6 * x + 2x * x)) = 720
(-36 + 12x + (-6x + 2x2)) = 720

Combine like terms: 12x + -6x = 6x
(-36 + 6x + 2x2) = 720

Solving
-36 + 6x + 2x2 = 720

Solving for variable 'x'.

Reorder the terms:
-36 + -720 + 6x + 2x2 = 720 + -720

Combine like terms: -36 + -720 = -756
-756 + 6x + 2x2 = 720 + -720

Combine like terms: 720 + -720 = 0
-756 + 6x + 2x2 = 0

Factor out the Greatest Common Factor (GCF), '2'.
2(-378 + 3x + x2) = 0

Factor a trinomial.
2((-21 + -1x)(18 + -1x)) = 0

Ignore the factor 2.
Subproblem 1
Set the factor '(-21 + -1x)' equal to zero and attempt to solve:

Simplifying
-21 + -1x = 0

Solving
-21 + -1x = 0

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

Add '21' to each side of the equation.
-21 + 21 + -1x = 0 + 21

Combine like terms: -21 + 21 = 0
0 + -1x = 0 + 21
-1x = 0 + 21

Combine like terms: 0 + 21 = 21
-1x = 21

Divide each side by '-1'.
x = -21

Simplifying
x = -21
Subproblem 2
Set the factor '(18 + -1x)' equal to zero and attempt to solve:

Simplifying
18 + -1x = 0

Solving
18 + -1x = 0

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

Add '-18' to each side of the equation.
18 + -18 + -1x = 0 + -18

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

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

Divide each side by '-1'.
x = 18

Simplifying
x = 18
Solution
x = {-21, 18}