u^2-2u-20=0

Solution for u^2-2u-20=0 equation:

Simplifying
u2 + -2u + -20 = 0

Reorder the terms:
-20 + -2u + u2 = 0

Solving
-20 + -2u + u2 = 0

Solving for variable 'u'.

Begin completing the square.

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -2u + 20 + u2 = 0 + 20

Reorder the terms:
-20 + 20 + -2u + u2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -2u + u2 = 0 + 20
-2u + u2 = 0 + 20

Combine like terms: 0 + 20 = 20
-2u + u2 = 20

The u term is -2u.  Take half its coefficient (-1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
-2u + 1 + u2 = 20 + 1

Reorder the terms:
1 + -2u + u2 = 20 + 1

Combine like terms: 20 + 1 = 21
1 + -2u + u2 = 21

Factor a perfect square on the left side:
(u + -1)(u + -1) = 21

Calculate the square root of the right side: 4.582575695

Break this problem into two subproblems by setting 
(u + -1) equal to 4.582575695 and -4.582575695.

Subproblem 1
u + -1 = 4.582575695

Simplifying
u + -1 = 4.582575695

Reorder the terms:
-1 + u = 4.582575695

Solving
-1 + u = 4.582575695

Solving for variable 'u'.

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

Add '1' to each side of the equation.
-1 + 1 + u = 4.582575695 + 1

Combine like terms: -1 + 1 = 0
0 + u = 4.582575695 + 1
u = 4.582575695 + 1

Combine like terms: 4.582575695 + 1 = 5.582575695
u = 5.582575695

Simplifying
u = 5.582575695

Subproblem 2
u + -1 = -4.582575695

Simplifying
u + -1 = -4.582575695

Reorder the terms:
-1 + u = -4.582575695

Solving
-1 + u = -4.582575695

Solving for variable 'u'.

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

Add '1' to each side of the equation.
-1 + 1 + u = -4.582575695 + 1

Combine like terms: -1 + 1 = 0
0 + u = -4.582575695 + 1
u = -4.582575695 + 1

Combine like terms: -4.582575695 + 1 = -3.582575695
u = -3.582575695

Simplifying
u = -3.582575695

Solution
The solution to the problem is based on the solutions
from the subproblems.
u = {5.582575695, -3.582575695}