x^2+15x-128=0

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Solution for x^2+15x-128=0 equation:


Simplifying
x2 + 15x + -128 = 0

Reorder the terms:
-128 + 15x + x2 = 0

Solving
-128 + 15x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '128' to each side of the equation.
-128 + 15x + 128 + x2 = 0 + 128

Reorder the terms:
-128 + 128 + 15x + x2 = 0 + 128

Combine like terms: -128 + 128 = 0
0 + 15x + x2 = 0 + 128
15x + x2 = 0 + 128

Combine like terms: 0 + 128 = 128
15x + x2 = 128

The x term is 15x.  Take half its coefficient (7.5).
Square it (56.25) and add it to both sides.

Add '56.25' to each side of the equation.
15x + 56.25 + x2 = 128 + 56.25

Reorder the terms:
56.25 + 15x + x2 = 128 + 56.25

Combine like terms: 128 + 56.25 = 184.25
56.25 + 15x + x2 = 184.25

Factor a perfect square on the left side:
(x + 7.5)(x + 7.5) = 184.25

Calculate the square root of the right side: 13.57387196

Break this problem into two subproblems by setting 
(x + 7.5) equal to 13.57387196 and -13.57387196.

Subproblem 1

x + 7.5 = 13.57387196 Simplifying x + 7.5 = 13.57387196 Reorder the terms: 7.5 + x = 13.57387196 Solving 7.5 + x = 13.57387196 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-7.5' to each side of the equation. 7.5 + -7.5 + x = 13.57387196 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = 13.57387196 + -7.5 x = 13.57387196 + -7.5 Combine like terms: 13.57387196 + -7.5 = 6.07387196 x = 6.07387196 Simplifying x = 6.07387196

Subproblem 2

x + 7.5 = -13.57387196 Simplifying x + 7.5 = -13.57387196 Reorder the terms: 7.5 + x = -13.57387196 Solving 7.5 + x = -13.57387196 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-7.5' to each side of the equation. 7.5 + -7.5 + x = -13.57387196 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = -13.57387196 + -7.5 x = -13.57387196 + -7.5 Combine like terms: -13.57387196 + -7.5 = -21.07387196 x = -21.07387196 Simplifying x = -21.07387196

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.07387196, -21.07387196}

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