(5x)(x-1)=20

Solution for (5x)(x-1)=20 equation:

Simplifying
(5x)(x + -1) = 20

Remove parenthesis around (5x)
5x(x + -1) = 20

Reorder the terms:
5x(-1 + x) = 20
(-1 * 5x + x * 5x) = 20
(-5x + 5x2) = 20

Solving
-5x + 5x2 = 20

Solving for variable 'x'.

Reorder the terms:
-20 + -5x + 5x2 = 20 + -20

Combine like terms: 20 + -20 = 0
-20 + -5x + 5x2 = 0

Factor out the Greatest Common Factor (GCF), '5'.
5(-4 + -1x + x2) = 0

Ignore the factor 5.
Subproblem 1
Set the factor '(-4 + -1x + x2)' equal to zero and attempt to solve:

Simplifying
-4 + -1x + x2 = 0

Solving
-4 + -1x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -1x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + -1x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -1x + x2 = 0 + 4
-1x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
-1x + x2 = 4

The x term is -1x.  Take half its coefficient (-0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1x + 0.25 + x2 = 4 + 0.25

Reorder the terms:
0.25 + -1x + x2 = 4 + 0.25

Combine like terms: 4 + 0.25 = 4.25
0.25 + -1x + x2 = 4.25

Factor a perfect square on the left side:
(x + -0.5)(x + -0.5) = 4.25

Calculate the square root of the right side: 2.061552813

Break this problem into two subproblems by setting 
(x + -0.5) equal to 2.061552813 and -2.061552813.

Subproblem 1
x + -0.5 = 2.061552813

Simplifying
x + -0.5 = 2.061552813

Reorder the terms:
-0.5 + x = 2.061552813

Solving
-0.5 + x = 2.061552813

Solving for variable 'x'.

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

Add '0.5' to each side of the equation.
-0.5 + 0.5 + x = 2.061552813 + 0.5

Combine like terms: -0.5 + 0.5 = 0.0
0.0 + x = 2.061552813 + 0.5
x = 2.061552813 + 0.5

Combine like terms: 2.061552813 + 0.5 = 2.561552813
x = 2.561552813

Simplifying
x = 2.561552813

Subproblem 2
x + -0.5 = -2.061552813

Simplifying
x + -0.5 = -2.061552813

Reorder the terms:
-0.5 + x = -2.061552813

Solving
-0.5 + x = -2.061552813

Solving for variable 'x'.

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

Add '0.5' to each side of the equation.
-0.5 + 0.5 + x = -2.061552813 + 0.5

Combine like terms: -0.5 + 0.5 = 0.0
0.0 + x = -2.061552813 + 0.5
x = -2.061552813 + 0.5

Combine like terms: -2.061552813 + 0.5 = -1.561552813
x = -1.561552813

Simplifying
x = -1.561552813

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {2.561552813, -1.561552813}
Solution
x = {2.561552813, -1.561552813}