(20+x)(20-x)=0

Solution for (20+x)(20-x)=0 equation:

Simplifying
(20 + x)(20 + -1x) = 0

Multiply (20 + x) * (20 + -1x)
(20(20 + -1x) + x(20 + -1x)) = 0
((20 * 20 + -1x * 20) + x(20 + -1x)) = 0
((400 + -20x) + x(20 + -1x)) = 0
(400 + -20x + (20 * x + -1x * x)) = 0
(400 + -20x + (20x + -1x2)) = 0

Combine like terms: -20x + 20x = 0
(400 + 0 + -1x2) = 0
(400 + -1x2) = 0

Solving
400 + -1x2 = 0

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 + -1x2 = 0 + -400

Combine like terms: 400 + -400 = 0
0 + -1x2 = 0 + -400
-1x2 = 0 + -400

Combine like terms: 0 + -400 = -400
-1x2 = -400

Divide each side by '-1'.
x2 = 400

Simplifying
x2 = 400

Take the square root of each side:
x = {-20, 20}