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

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

Simplifying
(x + -2)(x + 2) = 21

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

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

Multiply (-2 + x) * (2 + x)
(-2(2 + x) + x(2 + x)) = 21
((2 * -2 + x * -2) + x(2 + x)) = 21
((-4 + -2x) + x(2 + x)) = 21
(-4 + -2x + (2 * x + x * x)) = 21
(-4 + -2x + (2x + x2)) = 21

Combine like terms: -2x + 2x = 0
(-4 + 0 + x2) = 21
(-4 + x2) = 21

Solving
-4 + x2 = 21

Solving for variable 'x'.

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

Add '4' to each side of the equation.
-4 + 4 + x2 = 21 + 4

Combine like terms: -4 + 4 = 0
0 + x2 = 21 + 4
x2 = 21 + 4

Combine like terms: 21 + 4 = 25
x2 = 25

Simplifying
x2 = 25

Take the square root of each side:
x = {-5, 5}