x^2+12x=15

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Solution for x^2+12x=15 equation:


Simplifying
x2 + 12x = 15

Reorder the terms:
12x + x2 = 15

Solving
12x + x2 = 15

Solving for variable 'x'.

Reorder the terms:
-15 + 12x + x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-15 + 12x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + 12x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + 12x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + 12x + x2 = 0 + 15
12x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
12x + x2 = 15

The x term is 12x.  Take half its coefficient (6).
Square it (36) and add it to both sides.

Add '36' to each side of the equation.
12x + 36 + x2 = 15 + 36

Reorder the terms:
36 + 12x + x2 = 15 + 36

Combine like terms: 15 + 36 = 51
36 + 12x + x2 = 51

Factor a perfect square on the left side:
(x + 6)(x + 6) = 51

Calculate the square root of the right side: 7.141428429

Break this problem into two subproblems by setting 
(x + 6) equal to 7.141428429 and -7.141428429.

Subproblem 1

x + 6 = 7.141428429 Simplifying x + 6 = 7.141428429 Reorder the terms: 6 + x = 7.141428429 Solving 6 + x = 7.141428429 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6' to each side of the equation. 6 + -6 + x = 7.141428429 + -6 Combine like terms: 6 + -6 = 0 0 + x = 7.141428429 + -6 x = 7.141428429 + -6 Combine like terms: 7.141428429 + -6 = 1.141428429 x = 1.141428429 Simplifying x = 1.141428429

Subproblem 2

x + 6 = -7.141428429 Simplifying x + 6 = -7.141428429 Reorder the terms: 6 + x = -7.141428429 Solving 6 + x = -7.141428429 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6' to each side of the equation. 6 + -6 + x = -7.141428429 + -6 Combine like terms: 6 + -6 = 0 0 + x = -7.141428429 + -6 x = -7.141428429 + -6 Combine like terms: -7.141428429 + -6 = -13.141428429 x = -13.141428429 Simplifying x = -13.141428429

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.141428429, -13.141428429}

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