(4x-20)(x+5)=0

Solution for (4x-20)(x+5)=0 equation:

Simplifying
(4x + -20)(x + 5) = 0

Reorder the terms:
(-20 + 4x)(x + 5) = 0

Reorder the terms:
(-20 + 4x)(5 + x) = 0

Multiply (-20 + 4x) * (5 + x)
(-20(5 + x) + 4x * (5 + x)) = 0
((5 * -20 + x * -20) + 4x * (5 + x)) = 0
((-100 + -20x) + 4x * (5 + x)) = 0
(-100 + -20x + (5 * 4x + x * 4x)) = 0
(-100 + -20x + (20x + 4x2)) = 0

Combine like terms: -20x + 20x = 0
(-100 + 0 + 4x2) = 0
(-100 + 4x2) = 0

Solving
-100 + 4x2 = 0

Solving for variable 'x'.

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

Add '100' to each side of the equation.
-100 + 100 + 4x2 = 0 + 100

Combine like terms: -100 + 100 = 0
0 + 4x2 = 0 + 100
4x2 = 0 + 100

Combine like terms: 0 + 100 = 100
4x2 = 100

Divide each side by '4'.
x2 = 25

Simplifying
x2 = 25

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