x^2-6x-81=90

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Solution for x^2-6x-81=90 equation:


Simplifying
x2 + -6x + -81 = 90

Reorder the terms:
-81 + -6x + x2 = 90

Solving
-81 + -6x + x2 = 90

Solving for variable 'x'.

Reorder the terms:
-81 + -90 + -6x + x2 = 90 + -90

Combine like terms: -81 + -90 = -171
-171 + -6x + x2 = 90 + -90

Combine like terms: 90 + -90 = 0
-171 + -6x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '171' to each side of the equation.
-171 + -6x + 171 + x2 = 0 + 171

Reorder the terms:
-171 + 171 + -6x + x2 = 0 + 171

Combine like terms: -171 + 171 = 0
0 + -6x + x2 = 0 + 171
-6x + x2 = 0 + 171

Combine like terms: 0 + 171 = 171
-6x + x2 = 171

The x term is -6x.  Take half its coefficient (-3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
-6x + 9 + x2 = 171 + 9

Reorder the terms:
9 + -6x + x2 = 171 + 9

Combine like terms: 171 + 9 = 180
9 + -6x + x2 = 180

Factor a perfect square on the left side:
(x + -3)(x + -3) = 180

Calculate the square root of the right side: 13.416407865

Break this problem into two subproblems by setting 
(x + -3) equal to 13.416407865 and -13.416407865.

Subproblem 1

x + -3 = 13.416407865 Simplifying x + -3 = 13.416407865 Reorder the terms: -3 + x = 13.416407865 Solving -3 + x = 13.416407865 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + x = 13.416407865 + 3 Combine like terms: -3 + 3 = 0 0 + x = 13.416407865 + 3 x = 13.416407865 + 3 Combine like terms: 13.416407865 + 3 = 16.416407865 x = 16.416407865 Simplifying x = 16.416407865

Subproblem 2

x + -3 = -13.416407865 Simplifying x + -3 = -13.416407865 Reorder the terms: -3 + x = -13.416407865 Solving -3 + x = -13.416407865 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3' to each side of the equation. -3 + 3 + x = -13.416407865 + 3 Combine like terms: -3 + 3 = 0 0 + x = -13.416407865 + 3 x = -13.416407865 + 3 Combine like terms: -13.416407865 + 3 = -10.416407865 x = -10.416407865 Simplifying x = -10.416407865

Solution

The solution to the problem is based on the solutions from the subproblems. x = {16.416407865, -10.416407865}

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