u^2-2u-6=0

Solution for u^2-2u-6=0 equation:

Simplifying
u2 + -2u + -6 = 0

Reorder the terms:
-6 + -2u + u2 = 0

Solving
-6 + -2u + u2 = 0

Solving for variable 'u'.

Begin completing the square.

Move the constant term to the right:

Add '6' to each side of the equation.
-6 + -2u + 6 + u2 = 0 + 6

Reorder the terms:
-6 + 6 + -2u + u2 = 0 + 6

Combine like terms: -6 + 6 = 0
0 + -2u + u2 = 0 + 6
-2u + u2 = 0 + 6

Combine like terms: 0 + 6 = 6
-2u + u2 = 6

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 = 6 + 1

Reorder the terms:
1 + -2u + u2 = 6 + 1

Combine like terms: 6 + 1 = 7
1 + -2u + u2 = 7

Factor a perfect square on the left side:
(u + -1)(u + -1) = 7

Calculate the square root of the right side: 2.645751311

Break this problem into two subproblems by setting 
(u + -1) equal to 2.645751311 and -2.645751311.

Subproblem 1
u + -1 = 2.645751311

Simplifying
u + -1 = 2.645751311

Reorder the terms:
-1 + u = 2.645751311

Solving
-1 + u = 2.645751311

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 = 2.645751311 + 1

Combine like terms: -1 + 1 = 0
0 + u = 2.645751311 + 1
u = 2.645751311 + 1

Combine like terms: 2.645751311 + 1 = 3.645751311
u = 3.645751311

Simplifying
u = 3.645751311

Subproblem 2
u + -1 = -2.645751311

Simplifying
u + -1 = -2.645751311

Reorder the terms:
-1 + u = -2.645751311

Solving
-1 + u = -2.645751311

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 = -2.645751311 + 1

Combine like terms: -1 + 1 = 0
0 + u = -2.645751311 + 1
u = -2.645751311 + 1

Combine like terms: -2.645751311 + 1 = -1.645751311
u = -1.645751311

Simplifying
u = -1.645751311

Solution
The solution to the problem is based on the solutions
from the subproblems.
u = {3.645751311, -1.645751311}