x^2+18x=-78

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Solution for x^2+18x=-78 equation:


Simplifying
x2 + 18x = -78

Reorder the terms:
18x + x2 = -78

Solving
18x + x2 = -78

Solving for variable 'x'.

Reorder the terms:
78 + 18x + x2 = -78 + 78

Combine like terms: -78 + 78 = 0
78 + 18x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-78' to each side of the equation.
78 + 18x + -78 + x2 = 0 + -78

Reorder the terms:
78 + -78 + 18x + x2 = 0 + -78

Combine like terms: 78 + -78 = 0
0 + 18x + x2 = 0 + -78
18x + x2 = 0 + -78

Combine like terms: 0 + -78 = -78
18x + x2 = -78

The x term is 18x.  Take half its coefficient (9).
Square it (81) and add it to both sides.

Add '81' to each side of the equation.
18x + 81 + x2 = -78 + 81

Reorder the terms:
81 + 18x + x2 = -78 + 81

Combine like terms: -78 + 81 = 3
81 + 18x + x2 = 3

Factor a perfect square on the left side:
(x + 9)(x + 9) = 3

Calculate the square root of the right side: 1.732050808

Break this problem into two subproblems by setting 
(x + 9) equal to 1.732050808 and -1.732050808.

Subproblem 1

x + 9 = 1.732050808 Simplifying x + 9 = 1.732050808 Reorder the terms: 9 + x = 1.732050808 Solving 9 + x = 1.732050808 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-9' to each side of the equation. 9 + -9 + x = 1.732050808 + -9 Combine like terms: 9 + -9 = 0 0 + x = 1.732050808 + -9 x = 1.732050808 + -9 Combine like terms: 1.732050808 + -9 = -7.267949192 x = -7.267949192 Simplifying x = -7.267949192

Subproblem 2

x + 9 = -1.732050808 Simplifying x + 9 = -1.732050808 Reorder the terms: 9 + x = -1.732050808 Solving 9 + x = -1.732050808 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-9' to each side of the equation. 9 + -9 + x = -1.732050808 + -9 Combine like terms: 9 + -9 = 0 0 + x = -1.732050808 + -9 x = -1.732050808 + -9 Combine like terms: -1.732050808 + -9 = -10.732050808 x = -10.732050808 Simplifying x = -10.732050808

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-7.267949192, -10.732050808}

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