(x-21)(x+21)=0

Solution for (x-21)(x+21)=0 equation:

Simplifying
(x + -21)(x + 21) = 0

Reorder the terms:
(-21 + x)(x + 21) = 0

Reorder the terms:
(-21 + x)(21 + x) = 0

Multiply (-21 + x) * (21 + x)
(-21(21 + x) + x(21 + x)) = 0
((21 * -21 + x * -21) + x(21 + x)) = 0
((-441 + -21x) + x(21 + x)) = 0
(-441 + -21x + (21 * x + x * x)) = 0
(-441 + -21x + (21x + x2)) = 0

Combine like terms: -21x + 21x = 0
(-441 + 0 + x2) = 0
(-441 + x2) = 0

Solving
-441 + x2 = 0

Solving for variable 'x'.

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

Add '441' to each side of the equation.
-441 + 441 + x2 = 0 + 441

Combine like terms: -441 + 441 = 0
0 + x2 = 0 + 441
x2 = 0 + 441

Combine like terms: 0 + 441 = 441
x2 = 441

Simplifying
x2 = 441

Take the square root of each side:
x = {-21, 21}