x^2+18x=8

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Solution for x^2+18x=8 equation:


Simplifying
x2 + 18x = 8

Reorder the terms:
18x + x2 = 8

Solving
18x + x2 = 8

Solving for variable 'x'.

Reorder the terms:
-8 + 18x + x2 = 8 + -8

Combine like terms: 8 + -8 = 0
-8 + 18x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + 18x + 8 + x2 = 0 + 8

Reorder the terms:
-8 + 8 + 18x + x2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + 18x + x2 = 0 + 8
18x + x2 = 0 + 8

Combine like terms: 0 + 8 = 8
18x + x2 = 8

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 = 8 + 81

Reorder the terms:
81 + 18x + x2 = 8 + 81

Combine like terms: 8 + 81 = 89
81 + 18x + x2 = 89

Factor a perfect square on the left side:
(x + 9)(x + 9) = 89

Calculate the square root of the right side: 9.433981132

Break this problem into two subproblems by setting 
(x + 9) equal to 9.433981132 and -9.433981132.

Subproblem 1

x + 9 = 9.433981132 Simplifying x + 9 = 9.433981132 Reorder the terms: 9 + x = 9.433981132 Solving 9 + x = 9.433981132 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 = 9.433981132 + -9 Combine like terms: 9 + -9 = 0 0 + x = 9.433981132 + -9 x = 9.433981132 + -9 Combine like terms: 9.433981132 + -9 = 0.433981132 x = 0.433981132 Simplifying x = 0.433981132

Subproblem 2

x + 9 = -9.433981132 Simplifying x + 9 = -9.433981132 Reorder the terms: 9 + x = -9.433981132 Solving 9 + x = -9.433981132 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 = -9.433981132 + -9 Combine like terms: 9 + -9 = 0 0 + x = -9.433981132 + -9 x = -9.433981132 + -9 Combine like terms: -9.433981132 + -9 = -18.433981132 x = -18.433981132 Simplifying x = -18.433981132

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.433981132, -18.433981132}

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