-16x^2+80x+20=0

Solution for -16x^2+80x+20=0 equation:

Simplifying
-16x2 + 80x + 20 = 0

Reorder the terms:
20 + 80x + -16x2 = 0

Solving
20 + 80x + -16x2 = 0

Solving for variable 'x'.

Factor out the Greatest Common Factor (GCF), '4'.
4(5 + 20x + -4x2) = 0

Ignore the factor 4.
Subproblem 1
Set the factor '(5 + 20x + -4x2)' equal to zero and attempt to solve:

Simplifying
5 + 20x + -4x2 = 0

Solving
5 + 20x + -4x2 = 0

Begin completing the square.  Divide all terms by
-4 the coefficient of the squared term: 

Divide each side by '-4'.
-1.25 + -5x + x2 = 0

Move the constant term to the right:

Add '1.25' to each side of the equation.
-1.25 + -5x + 1.25 + x2 = 0 + 1.25

Reorder the terms:
-1.25 + 1.25 + -5x + x2 = 0 + 1.25

Combine like terms: -1.25 + 1.25 = 0.00
0.00 + -5x + x2 = 0 + 1.25
-5x + x2 = 0 + 1.25

Combine like terms: 0 + 1.25 = 1.25
-5x + x2 = 1.25

The x term is -5x.  Take half its coefficient (-2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
-5x + 6.25 + x2 = 1.25 + 6.25

Reorder the terms:
6.25 + -5x + x2 = 1.25 + 6.25

Combine like terms: 1.25 + 6.25 = 7.5
6.25 + -5x + x2 = 7.5

Factor a perfect square on the left side:
(x + -2.5)(x + -2.5) = 7.5

Calculate the square root of the right side: 2.738612788

Break this problem into two subproblems by setting 
(x + -2.5) equal to 2.738612788 and -2.738612788.

Subproblem 1
x + -2.5 = 2.738612788

Simplifying
x + -2.5 = 2.738612788

Reorder the terms:
-2.5 + x = 2.738612788

Solving
-2.5 + x = 2.738612788

Solving for variable 'x'.

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

Add '2.5' to each side of the equation.
-2.5 + 2.5 + x = 2.738612788 + 2.5

Combine like terms: -2.5 + 2.5 = 0.0
0.0 + x = 2.738612788 + 2.5
x = 2.738612788 + 2.5

Combine like terms: 2.738612788 + 2.5 = 5.238612788
x = 5.238612788

Simplifying
x = 5.238612788

Subproblem 2
x + -2.5 = -2.738612788

Simplifying
x + -2.5 = -2.738612788

Reorder the terms:
-2.5 + x = -2.738612788

Solving
-2.5 + x = -2.738612788

Solving for variable 'x'.

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

Add '2.5' to each side of the equation.
-2.5 + 2.5 + x = -2.738612788 + 2.5

Combine like terms: -2.5 + 2.5 = 0.0
0.0 + x = -2.738612788 + 2.5
x = -2.738612788 + 2.5

Combine like terms: -2.738612788 + 2.5 = -0.238612788
x = -0.238612788

Simplifying
x = -0.238612788

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {5.238612788, -0.238612788}
Solution
x = {5.238612788, -0.238612788}