2x^2-6x-81=0

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Solution for 2x^2-6x-81=0 equation:


Simplifying
2x2 + -6x + -81 = 0

Reorder the terms:
-81 + -6x + 2x2 = 0

Solving
-81 + -6x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-40.5 + -3x + x2 = 0

Move the constant term to the right:

Add '40.5' to each side of the equation.
-40.5 + -3x + 40.5 + x2 = 0 + 40.5

Reorder the terms:
-40.5 + 40.5 + -3x + x2 = 0 + 40.5

Combine like terms: -40.5 + 40.5 = 0.0
0.0 + -3x + x2 = 0 + 40.5
-3x + x2 = 0 + 40.5

Combine like terms: 0 + 40.5 = 40.5
-3x + x2 = 40.5

The x term is -3x.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3x + 2.25 + x2 = 40.5 + 2.25

Reorder the terms:
2.25 + -3x + x2 = 40.5 + 2.25

Combine like terms: 40.5 + 2.25 = 42.75
2.25 + -3x + x2 = 42.75

Factor a perfect square on the left side:
(x + -1.5)(x + -1.5) = 42.75

Calculate the square root of the right side: 6.538348415

Break this problem into two subproblems by setting 
(x + -1.5) equal to 6.538348415 and -6.538348415.

Subproblem 1

x + -1.5 = 6.538348415 Simplifying x + -1.5 = 6.538348415 Reorder the terms: -1.5 + x = 6.538348415 Solving -1.5 + x = 6.538348415 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x = 6.538348415 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = 6.538348415 + 1.5 x = 6.538348415 + 1.5 Combine like terms: 6.538348415 + 1.5 = 8.038348415 x = 8.038348415 Simplifying x = 8.038348415

Subproblem 2

x + -1.5 = -6.538348415 Simplifying x + -1.5 = -6.538348415 Reorder the terms: -1.5 + x = -6.538348415 Solving -1.5 + x = -6.538348415 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x = -6.538348415 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = -6.538348415 + 1.5 x = -6.538348415 + 1.5 Combine like terms: -6.538348415 + 1.5 = -5.038348415 x = -5.038348415 Simplifying x = -5.038348415

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.038348415, -5.038348415}

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