x^2+12x=42

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Solution for x^2+12x=42 equation:


Simplifying
x2 + 12x = 42

Reorder the terms:
12x + x2 = 42

Solving
12x + x2 = 42

Solving for variable 'x'.

Reorder the terms:
-42 + 12x + x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-42 + 12x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '42' to each side of the equation.
-42 + 12x + 42 + x2 = 0 + 42

Reorder the terms:
-42 + 42 + 12x + x2 = 0 + 42

Combine like terms: -42 + 42 = 0
0 + 12x + x2 = 0 + 42
12x + x2 = 0 + 42

Combine like terms: 0 + 42 = 42
12x + x2 = 42

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 = 42 + 36

Reorder the terms:
36 + 12x + x2 = 42 + 36

Combine like terms: 42 + 36 = 78
36 + 12x + x2 = 78

Factor a perfect square on the left side:
(x + 6)(x + 6) = 78

Calculate the square root of the right side: 8.831760866

Break this problem into two subproblems by setting 
(x + 6) equal to 8.831760866 and -8.831760866.

Subproblem 1

x + 6 = 8.831760866 Simplifying x + 6 = 8.831760866 Reorder the terms: 6 + x = 8.831760866 Solving 6 + x = 8.831760866 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 = 8.831760866 + -6 Combine like terms: 6 + -6 = 0 0 + x = 8.831760866 + -6 x = 8.831760866 + -6 Combine like terms: 8.831760866 + -6 = 2.831760866 x = 2.831760866 Simplifying x = 2.831760866

Subproblem 2

x + 6 = -8.831760866 Simplifying x + 6 = -8.831760866 Reorder the terms: 6 + x = -8.831760866 Solving 6 + x = -8.831760866 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 = -8.831760866 + -6 Combine like terms: 6 + -6 = 0 0 + x = -8.831760866 + -6 x = -8.831760866 + -6 Combine like terms: -8.831760866 + -6 = -14.831760866 x = -14.831760866 Simplifying x = -14.831760866

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.831760866, -14.831760866}

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