x^2+15x=12

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


Simplifying
x2 + 15x = 12

Reorder the terms:
15x + x2 = 12

Solving
15x + x2 = 12

Solving for variable 'x'.

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

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

Begin completing the square.

Move the constant term to the right:

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

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

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

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

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 = 12 + 56.25

Reorder the terms:
56.25 + 15x + x2 = 12 + 56.25

Combine like terms: 12 + 56.25 = 68.25
56.25 + 15x + x2 = 68.25

Factor a perfect square on the left side:
(x + 7.5)(x + 7.5) = 68.25

Calculate the square root of the right side: 8.261355821

Break this problem into two subproblems by setting 
(x + 7.5) equal to 8.261355821 and -8.261355821.

Subproblem 1

x + 7.5 = 8.261355821 Simplifying x + 7.5 = 8.261355821 Reorder the terms: 7.5 + x = 8.261355821 Solving 7.5 + x = 8.261355821 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 = 8.261355821 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = 8.261355821 + -7.5 x = 8.261355821 + -7.5 Combine like terms: 8.261355821 + -7.5 = 0.761355821 x = 0.761355821 Simplifying x = 0.761355821

Subproblem 2

x + 7.5 = -8.261355821 Simplifying x + 7.5 = -8.261355821 Reorder the terms: 7.5 + x = -8.261355821 Solving 7.5 + x = -8.261355821 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 = -8.261355821 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = -8.261355821 + -7.5 x = -8.261355821 + -7.5 Combine like terms: -8.261355821 + -7.5 = -15.761355821 x = -15.761355821 Simplifying x = -15.761355821

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.761355821, -15.761355821}

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