x^2-18x-9=0

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Solution for x^2-18x-9=0 equation:


Simplifying
x2 + -18x + -9 = 0

Reorder the terms:
-9 + -18x + x2 = 0

Solving
-9 + -18x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + -18x + 9 + x2 = 0 + 9

Reorder the terms:
-9 + 9 + -18x + x2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + -18x + x2 = 0 + 9
-18x + x2 = 0 + 9

Combine like terms: 0 + 9 = 9
-18x + x2 = 9

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 = 9 + 81

Reorder the terms:
81 + -18x + x2 = 9 + 81

Combine like terms: 9 + 81 = 90
81 + -18x + x2 = 90

Factor a perfect square on the left side:
(x + -9)(x + -9) = 90

Calculate the square root of the right side: 9.486832981

Break this problem into two subproblems by setting 
(x + -9) equal to 9.486832981 and -9.486832981.

Subproblem 1

x + -9 = 9.486832981 Simplifying x + -9 = 9.486832981 Reorder the terms: -9 + x = 9.486832981 Solving -9 + x = 9.486832981 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 = 9.486832981 + 9 Combine like terms: -9 + 9 = 0 0 + x = 9.486832981 + 9 x = 9.486832981 + 9 Combine like terms: 9.486832981 + 9 = 18.486832981 x = 18.486832981 Simplifying x = 18.486832981

Subproblem 2

x + -9 = -9.486832981 Simplifying x + -9 = -9.486832981 Reorder the terms: -9 + x = -9.486832981 Solving -9 + x = -9.486832981 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 = -9.486832981 + 9 Combine like terms: -9 + 9 = 0 0 + x = -9.486832981 + 9 x = -9.486832981 + 9 Combine like terms: -9.486832981 + 9 = -0.486832981 x = -0.486832981 Simplifying x = -0.486832981

Solution

The solution to the problem is based on the solutions from the subproblems. x = {18.486832981, -0.486832981}

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