x^2+8x-126=0

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Solution for x^2+8x-126=0 equation:


Simplifying
x2 + 8x + -126 = 0

Reorder the terms:
-126 + 8x + x2 = 0

Solving
-126 + 8x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '126' to each side of the equation.
-126 + 8x + 126 + x2 = 0 + 126

Reorder the terms:
-126 + 126 + 8x + x2 = 0 + 126

Combine like terms: -126 + 126 = 0
0 + 8x + x2 = 0 + 126
8x + x2 = 0 + 126

Combine like terms: 0 + 126 = 126
8x + x2 = 126

The x term is 8x.  Take half its coefficient (4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
8x + 16 + x2 = 126 + 16

Reorder the terms:
16 + 8x + x2 = 126 + 16

Combine like terms: 126 + 16 = 142
16 + 8x + x2 = 142

Factor a perfect square on the left side:
(x + 4)(x + 4) = 142

Calculate the square root of the right side: 11.916375288

Break this problem into two subproblems by setting 
(x + 4) equal to 11.916375288 and -11.916375288.

Subproblem 1

x + 4 = 11.916375288 Simplifying x + 4 = 11.916375288 Reorder the terms: 4 + x = 11.916375288 Solving 4 + x = 11.916375288 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + x = 11.916375288 + -4 Combine like terms: 4 + -4 = 0 0 + x = 11.916375288 + -4 x = 11.916375288 + -4 Combine like terms: 11.916375288 + -4 = 7.916375288 x = 7.916375288 Simplifying x = 7.916375288

Subproblem 2

x + 4 = -11.916375288 Simplifying x + 4 = -11.916375288 Reorder the terms: 4 + x = -11.916375288 Solving 4 + x = -11.916375288 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + x = -11.916375288 + -4 Combine like terms: 4 + -4 = 0 0 + x = -11.916375288 + -4 x = -11.916375288 + -4 Combine like terms: -11.916375288 + -4 = -15.916375288 x = -15.916375288 Simplifying x = -15.916375288

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.916375288, -15.916375288}

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