-x^2-11x+18=0

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Solution for -x^2-11x+18=0 equation: 


Simplifying
-1x2 + -11x + 18 = 0

Reorder the terms:
18 + -11x + -1x2 = 0

Solving
18 + -11x + -1x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-18 + 11x + x2 = 0

Move the constant term to the right:

Add '18' to each side of the equation.
-18 + 11x + 18 + x2 = 0 + 18

Reorder the terms:
-18 + 18 + 11x + x2 = 0 + 18

Combine like terms: -18 + 18 = 0
0 + 11x + x2 = 0 + 18
11x + x2 = 0 + 18

Combine like terms: 0 + 18 = 18
11x + x2 = 18

The x term is 11x.  Take half its coefficient (5.5).
Square it (30.25) and add it to both sides.

Add '30.25' to each side of the equation.
11x + 30.25 + x2 = 18 + 30.25

Reorder the terms:
30.25 + 11x + x2 = 18 + 30.25

Combine like terms: 18 + 30.25 = 48.25
30.25 + 11x + x2 = 48.25

Factor a perfect square on the left side:
(x + 5.5)(x + 5.5) = 48.25

Calculate the square root of the right side: 6.946221995

Break this problem into two subproblems by setting 
(x + 5.5) equal to 6.946221995 and -6.946221995.


Subproblem 1
x + 5.5 = 6.946221995

Simplifying
x + 5.5 = 6.946221995

Reorder the terms:
5.5 + x = 6.946221995

Solving
5.5 + x = 6.946221995

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-5.5' to each side of the equation.
5.5 + -5.5 + x = 6.946221995 + -5.5

Combine like terms: 5.5 + -5.5 = 0.0
0.0 + x = 6.946221995 + -5.5
x = 6.946221995 + -5.5

Combine like terms: 6.946221995 + -5.5 = 1.446221995
x = 1.446221995

Simplifying
x = 1.446221995


Subproblem 2
x + 5.5 = -6.946221995

Simplifying
x + 5.5 = -6.946221995

Reorder the terms:
5.5 + x = -6.946221995

Solving
5.5 + x = -6.946221995

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-5.5' to each side of the equation.
5.5 + -5.5 + x = -6.946221995 + -5.5

Combine like terms: 5.5 + -5.5 = 0.0
0.0 + x = -6.946221995 + -5.5
x = -6.946221995 + -5.5

Combine like terms: -6.946221995 + -5.5 = -12.446221995
x = -12.446221995

Simplifying
x = -12.446221995


Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {1.446221995, -12.446221995}

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