(x-20)(x+20)=40

Solution for (x-20)(x+20)=40 equation:

Simplifying
(x + -20)(x + 20) = 40

Reorder the terms:
(-20 + x)(x + 20) = 40

Reorder the terms:
(-20 + x)(20 + x) = 40

Multiply (-20 + x) * (20 + x)
(-20(20 + x) + x(20 + x)) = 40
((20 * -20 + x * -20) + x(20 + x)) = 40
((-400 + -20x) + x(20 + x)) = 40
(-400 + -20x + (20 * x + x * x)) = 40
(-400 + -20x + (20x + x2)) = 40

Combine like terms: -20x + 20x = 0
(-400 + 0 + x2) = 40
(-400 + x2) = 40

Solving
-400 + x2 = 40

Solving for variable 'x'.

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

Add '400' to each side of the equation.
-400 + 400 + x2 = 40 + 400

Combine like terms: -400 + 400 = 0
0 + x2 = 40 + 400
x2 = 40 + 400

Combine like terms: 40 + 400 = 440
x2 = 440

Simplifying
x2 = 440

Take the square root of each side:
x = {-20.976176963, 20.976176963}