(2x-1)(x+1)=-x^2-12x+5

Solution for (2x-1)(x+1)=-x^2-12x+5 equation:

Simplifying
(2x + -1)(x + 1) = -1x2 + -12x + 5

Reorder the terms:
(-1 + 2x)(x + 1) = -1x2 + -12x + 5

Reorder the terms:
(-1 + 2x)(1 + x) = -1x2 + -12x + 5

Multiply (-1 + 2x) * (1 + x)
(-1(1 + x) + 2x * (1 + x)) = -1x2 + -12x + 5
((1 * -1 + x * -1) + 2x * (1 + x)) = -1x2 + -12x + 5
((-1 + -1x) + 2x * (1 + x)) = -1x2 + -12x + 5
(-1 + -1x + (1 * 2x + x * 2x)) = -1x2 + -12x + 5
(-1 + -1x + (2x + 2x2)) = -1x2 + -12x + 5

Combine like terms: -1x + 2x = 1x
(-1 + 1x + 2x2) = -1x2 + -12x + 5

Reorder the terms:
-1 + 1x + 2x2 = 5 + -12x + -1x2

Solving
-1 + 1x + 2x2 = 5 + -12x + -1x2

Solving for variable 'x'.

Reorder the terms:
-1 + -5 + 1x + 12x + 2x2 + x2 = 5 + -12x + -1x2 + -5 + 12x + x2

Combine like terms: -1 + -5 = -6
-6 + 1x + 12x + 2x2 + x2 = 5 + -12x + -1x2 + -5 + 12x + x2

Combine like terms: 1x + 12x = 13x
-6 + 13x + 2x2 + x2 = 5 + -12x + -1x2 + -5 + 12x + x2

Combine like terms: 2x2 + x2 = 3x2
-6 + 13x + 3x2 = 5 + -12x + -1x2 + -5 + 12x + x2

Reorder the terms:
-6 + 13x + 3x2 = 5 + -5 + -12x + 12x + -1x2 + x2

Combine like terms: 5 + -5 = 0
-6 + 13x + 3x2 = 0 + -12x + 12x + -1x2 + x2
-6 + 13x + 3x2 = -12x + 12x + -1x2 + x2

Combine like terms: -12x + 12x = 0
-6 + 13x + 3x2 = 0 + -1x2 + x2
-6 + 13x + 3x2 = -1x2 + x2

Combine like terms: -1x2 + x2 = 0
-6 + 13x + 3x2 = 0

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

Divide each side by '3'.
-2 + 4.333333333x + x2 = 0

Move the constant term to the right:

Add '2' to each side of the equation.
-2 + 4.333333333x + 2 + x2 = 0 + 2

Reorder the terms:
-2 + 2 + 4.333333333x + x2 = 0 + 2

Combine like terms: -2 + 2 = 0
0 + 4.333333333x + x2 = 0 + 2
4.333333333x + x2 = 0 + 2

Combine like terms: 0 + 2 = 2
4.333333333x + x2 = 2

The x term is 4.333333333x.  Take half its coefficient (2.166666667).
Square it (4.694444446) and add it to both sides.

Add '4.694444446' to each side of the equation.
4.333333333x + 4.694444446 + x2 = 2 + 4.694444446

Reorder the terms:
4.694444446 + 4.333333333x + x2 = 2 + 4.694444446

Combine like terms: 2 + 4.694444446 = 6.694444446
4.694444446 + 4.333333333x + x2 = 6.694444446

Factor a perfect square on the left side:
(x + 2.166666667)(x + 2.166666667) = 6.694444446

Calculate the square root of the right side: 2.58736245

Break this problem into two subproblems by setting 
(x + 2.166666667) equal to 2.58736245 and -2.58736245.

Subproblem 1
x + 2.166666667 = 2.58736245

Simplifying
x + 2.166666667 = 2.58736245

Reorder the terms:
2.166666667 + x = 2.58736245

Solving
2.166666667 + x = 2.58736245

Solving for variable 'x'.

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

Add '-2.166666667' to each side of the equation.
2.166666667 + -2.166666667 + x = 2.58736245 + -2.166666667

Combine like terms: 2.166666667 + -2.166666667 = 0.000000000
0.000000000 + x = 2.58736245 + -2.166666667
x = 2.58736245 + -2.166666667

Combine like terms: 2.58736245 + -2.166666667 = 0.420695783
x = 0.420695783

Simplifying
x = 0.420695783

Subproblem 2
x + 2.166666667 = -2.58736245

Simplifying
x + 2.166666667 = -2.58736245

Reorder the terms:
2.166666667 + x = -2.58736245

Solving
2.166666667 + x = -2.58736245

Solving for variable 'x'.

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

Add '-2.166666667' to each side of the equation.
2.166666667 + -2.166666667 + x = -2.58736245 + -2.166666667

Combine like terms: 2.166666667 + -2.166666667 = 0.000000000
0.000000000 + x = -2.58736245 + -2.166666667
x = -2.58736245 + -2.166666667

Combine like terms: -2.58736245 + -2.166666667 = -4.754029117
x = -4.754029117

Simplifying
x = -4.754029117

Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {0.420695783, -4.754029117}