x^2+8x=120

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Solution for x^2+8x=120 equation:


Simplifying
x2 + 8x = 120

Reorder the terms:
8x + x2 = 120

Solving
8x + x2 = 120

Solving for variable 'x'.

Reorder the terms:
-120 + 8x + x2 = 120 + -120

Combine like terms: 120 + -120 = 0
-120 + 8x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '120' to each side of the equation.
-120 + 8x + 120 + x2 = 0 + 120

Reorder the terms:
-120 + 120 + 8x + x2 = 0 + 120

Combine like terms: -120 + 120 = 0
0 + 8x + x2 = 0 + 120
8x + x2 = 0 + 120

Combine like terms: 0 + 120 = 120
8x + x2 = 120

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 = 120 + 16

Reorder the terms:
16 + 8x + x2 = 120 + 16

Combine like terms: 120 + 16 = 136
16 + 8x + x2 = 136

Factor a perfect square on the left side:
(x + 4)(x + 4) = 136

Calculate the square root of the right side: 11.66190379

Break this problem into two subproblems by setting 
(x + 4) equal to 11.66190379 and -11.66190379.

Subproblem 1

x + 4 = 11.66190379 Simplifying x + 4 = 11.66190379 Reorder the terms: 4 + x = 11.66190379 Solving 4 + x = 11.66190379 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 = 11.66190379 + -4 Combine like terms: 4 + -4 = 0 0 + x = 11.66190379 + -4 x = 11.66190379 + -4 Combine like terms: 11.66190379 + -4 = 7.66190379 x = 7.66190379 Simplifying x = 7.66190379

Subproblem 2

x + 4 = -11.66190379 Simplifying x + 4 = -11.66190379 Reorder the terms: 4 + x = -11.66190379 Solving 4 + x = -11.66190379 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 = -11.66190379 + -4 Combine like terms: 4 + -4 = 0 0 + x = -11.66190379 + -4 x = -11.66190379 + -4 Combine like terms: -11.66190379 + -4 = -15.66190379 x = -15.66190379 Simplifying x = -15.66190379

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.66190379, -15.66190379}

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