(x-21)2=90

Solution for (x-21)2=90 equation:

Simplifying
(x + -21) * 2 = 90

Reorder the terms:
(-21 + x) * 2 = 90

Reorder the terms for easier multiplication:
2(-21 + x) = 90
(-21 * 2 + x * 2) = 90
(-42 + 2x) = 90

Solving
-42 + 2x = 90

Solving for variable 'x'.

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

Add '42' to each side of the equation.
-42 + 42 + 2x = 90 + 42

Combine like terms: -42 + 42 = 0
0 + 2x = 90 + 42
2x = 90 + 42

Combine like terms: 90 + 42 = 132
2x = 132

Divide each side by '2'.
x = 66

Simplifying
x = 66