x^2-18x-15=0

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Solution for x^2-18x-15=0 equation:


Simplifying
x2 + -18x + -15 = 0

Reorder the terms:
-15 + -18x + x2 = 0

Solving
-15 + -18x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + -18x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + -18x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + -18x + x2 = 0 + 15
-18x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
-18x + x2 = 15

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 = 15 + 81

Reorder the terms:
81 + -18x + x2 = 15 + 81

Combine like terms: 15 + 81 = 96
81 + -18x + x2 = 96

Factor a perfect square on the left side:
(x + -9)(x + -9) = 96

Calculate the square root of the right side: 9.797958971

Break this problem into two subproblems by setting 
(x + -9) equal to 9.797958971 and -9.797958971.

Subproblem 1

x + -9 = 9.797958971 Simplifying x + -9 = 9.797958971 Reorder the terms: -9 + x = 9.797958971 Solving -9 + x = 9.797958971 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 = 9.797958971 + 9 Combine like terms: -9 + 9 = 0 0 + x = 9.797958971 + 9 x = 9.797958971 + 9 Combine like terms: 9.797958971 + 9 = 18.797958971 x = 18.797958971 Simplifying x = 18.797958971

Subproblem 2

x + -9 = -9.797958971 Simplifying x + -9 = -9.797958971 Reorder the terms: -9 + x = -9.797958971 Solving -9 + x = -9.797958971 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 = -9.797958971 + 9 Combine like terms: -9 + 9 = 0 0 + x = -9.797958971 + 9 x = -9.797958971 + 9 Combine like terms: -9.797958971 + 9 = -0.797958971 x = -0.797958971 Simplifying x = -0.797958971

Solution

The solution to the problem is based on the solutions from the subproblems. x = {18.797958971, -0.797958971}

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