9x^2-12x-20=0

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Solution for 9x^2-12x-20=0 equation:


Simplifying
9x2 + -12x + -20 = 0

Reorder the terms:
-20 + -12x + 9x2 = 0

Solving
-20 + -12x + 9x2 = 0

Solving for variable 'x'.

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

Divide each side by '9'.
-2.222222222 + -1.333333333x + x2 = 0

Move the constant term to the right:

Add '2.222222222' to each side of the equation.
-2.222222222 + -1.333333333x + 2.222222222 + x2 = 0 + 2.222222222

Reorder the terms:
-2.222222222 + 2.222222222 + -1.333333333x + x2 = 0 + 2.222222222

Combine like terms: -2.222222222 + 2.222222222 = 0.000000000
0.000000000 + -1.333333333x + x2 = 0 + 2.222222222
-1.333333333x + x2 = 0 + 2.222222222

Combine like terms: 0 + 2.222222222 = 2.222222222
-1.333333333x + x2 = 2.222222222

The x term is -1.333333333x.  Take half its coefficient (-0.6666666665).
Square it (0.4444444442) and add it to both sides.

Add '0.4444444442' to each side of the equation.
-1.333333333x + 0.4444444442 + x2 = 2.222222222 + 0.4444444442

Reorder the terms:
0.4444444442 + -1.333333333x + x2 = 2.222222222 + 0.4444444442

Combine like terms: 2.222222222 + 0.4444444442 = 2.6666666662
0.4444444442 + -1.333333333x + x2 = 2.6666666662

Factor a perfect square on the left side:
(x + -0.6666666665)(x + -0.6666666665) = 2.6666666662

Calculate the square root of the right side: 1.632993162

Break this problem into two subproblems by setting 
(x + -0.6666666665) equal to 1.632993162 and -1.632993162.

Subproblem 1

x + -0.6666666665 = 1.632993162 Simplifying x + -0.6666666665 = 1.632993162 Reorder the terms: -0.6666666665 + x = 1.632993162 Solving -0.6666666665 + x = 1.632993162 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.6666666665' to each side of the equation. -0.6666666665 + 0.6666666665 + x = 1.632993162 + 0.6666666665 Combine like terms: -0.6666666665 + 0.6666666665 = 0.0000000000 0.0000000000 + x = 1.632993162 + 0.6666666665 x = 1.632993162 + 0.6666666665 Combine like terms: 1.632993162 + 0.6666666665 = 2.2996598285 x = 2.2996598285 Simplifying x = 2.2996598285

Subproblem 2

x + -0.6666666665 = -1.632993162 Simplifying x + -0.6666666665 = -1.632993162 Reorder the terms: -0.6666666665 + x = -1.632993162 Solving -0.6666666665 + x = -1.632993162 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.6666666665' to each side of the equation. -0.6666666665 + 0.6666666665 + x = -1.632993162 + 0.6666666665 Combine like terms: -0.6666666665 + 0.6666666665 = 0.0000000000 0.0000000000 + x = -1.632993162 + 0.6666666665 x = -1.632993162 + 0.6666666665 Combine like terms: -1.632993162 + 0.6666666665 = -0.9663264955 x = -0.9663264955 Simplifying x = -0.9663264955

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.2996598285, -0.9663264955}

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