(2x+3)2-(x+6)2=21

Solution for (2x+3)2-(x+6)2=21 equation:

Simplifying
(2x + 3) * 2 + -1(x + 6) * 2 = 21

Reorder the terms:
(3 + 2x) * 2 + -1(x + 6) * 2 = 21

Reorder the terms for easier multiplication:
2(3 + 2x) + -1(x + 6) * 2 = 21
(3 * 2 + 2x * 2) + -1(x + 6) * 2 = 21
(6 + 4x) + -1(x + 6) * 2 = 21

Reorder the terms:
6 + 4x + -1(6 + x) * 2 = 21

Reorder the terms for easier multiplication:
6 + 4x + -1 * 2(6 + x) = 21

Multiply -1 * 2
6 + 4x + -2(6 + x) = 21
6 + 4x + (6 * -2 + x * -2) = 21
6 + 4x + (-12 + -2x) = 21

Reorder the terms:
6 + -12 + 4x + -2x = 21

Combine like terms: 6 + -12 = -6
-6 + 4x + -2x = 21

Combine like terms: 4x + -2x = 2x
-6 + 2x = 21

Solving
-6 + 2x = 21

Solving for variable 'x'.

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

Add '6' to each side of the equation.
-6 + 6 + 2x = 21 + 6

Combine like terms: -6 + 6 = 0
0 + 2x = 21 + 6
2x = 21 + 6

Combine like terms: 21 + 6 = 27
2x = 27

Divide each side by '2'.
x = 13.5

Simplifying
x = 13.5