x^2+18x-78=0

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Solution for x^2+18x-78=0 equation:


Simplifying
x2 + 18x + -78 = 0

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

Solving
-78 + 18x + x2 = 0

Solving for variable 'x'.

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 = 159
81 + 18x + x2 = 159

Factor a perfect square on the left side:
(x + 9)(x + 9) = 159

Calculate the square root of the right side: 12.609520213

Break this problem into two subproblems by setting 
(x + 9) equal to 12.609520213 and -12.609520213.

Subproblem 1

x + 9 = 12.609520213 Simplifying x + 9 = 12.609520213 Reorder the terms: 9 + x = 12.609520213 Solving 9 + x = 12.609520213 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 = 12.609520213 + -9 Combine like terms: 9 + -9 = 0 0 + x = 12.609520213 + -9 x = 12.609520213 + -9 Combine like terms: 12.609520213 + -9 = 3.609520213 x = 3.609520213 Simplifying x = 3.609520213

Subproblem 2

x + 9 = -12.609520213 Simplifying x + 9 = -12.609520213 Reorder the terms: 9 + x = -12.609520213 Solving 9 + x = -12.609520213 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 = -12.609520213 + -9 Combine like terms: 9 + -9 = 0 0 + x = -12.609520213 + -9 x = -12.609520213 + -9 Combine like terms: -12.609520213 + -9 = -21.609520213 x = -21.609520213 Simplifying x = -21.609520213

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.609520213, -21.609520213}

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