x^2+2x=128

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Solution for x^2+2x=128 equation:


Simplifying
x2 + 2x = 128

Reorder the terms:
2x + x2 = 128

Solving
2x + x2 = 128

Solving for variable 'x'.

Reorder the terms:
-128 + 2x + x2 = 128 + -128

Combine like terms: 128 + -128 = 0
-128 + 2x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '128' to each side of the equation.
-128 + 2x + 128 + x2 = 0 + 128

Reorder the terms:
-128 + 128 + 2x + x2 = 0 + 128

Combine like terms: -128 + 128 = 0
0 + 2x + x2 = 0 + 128
2x + x2 = 0 + 128

Combine like terms: 0 + 128 = 128
2x + x2 = 128

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

Add '1' to each side of the equation.
2x + 1 + x2 = 128 + 1

Reorder the terms:
1 + 2x + x2 = 128 + 1

Combine like terms: 128 + 1 = 129
1 + 2x + x2 = 129

Factor a perfect square on the left side:
(x + 1)(x + 1) = 129

Calculate the square root of the right side: 11.357816692

Break this problem into two subproblems by setting 
(x + 1) equal to 11.357816692 and -11.357816692.

Subproblem 1

x + 1 = 11.357816692 Simplifying x + 1 = 11.357816692 Reorder the terms: 1 + x = 11.357816692 Solving 1 + x = 11.357816692 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = 11.357816692 + -1 Combine like terms: 1 + -1 = 0 0 + x = 11.357816692 + -1 x = 11.357816692 + -1 Combine like terms: 11.357816692 + -1 = 10.357816692 x = 10.357816692 Simplifying x = 10.357816692

Subproblem 2

x + 1 = -11.357816692 Simplifying x + 1 = -11.357816692 Reorder the terms: 1 + x = -11.357816692 Solving 1 + x = -11.357816692 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = -11.357816692 + -1 Combine like terms: 1 + -1 = 0 0 + x = -11.357816692 + -1 x = -11.357816692 + -1 Combine like terms: -11.357816692 + -1 = -12.357816692 x = -12.357816692 Simplifying x = -12.357816692

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.357816692, -12.357816692}

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