9x^2-72x-128=0

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Solution for 9x^2-72x-128=0 equation:


Simplifying
9x2 + -72x + -128 = 0

Reorder the terms:
-128 + -72x + 9x2 = 0

Solving
-128 + -72x + 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'.
-14.22222222 + -8x + x2 = 0

Move the constant term to the right:

Add '14.22222222' to each side of the equation.
-14.22222222 + -8x + 14.22222222 + x2 = 0 + 14.22222222

Reorder the terms:
-14.22222222 + 14.22222222 + -8x + x2 = 0 + 14.22222222

Combine like terms: -14.22222222 + 14.22222222 = 0.00000000
0.00000000 + -8x + x2 = 0 + 14.22222222
-8x + x2 = 0 + 14.22222222

Combine like terms: 0 + 14.22222222 = 14.22222222
-8x + x2 = 14.22222222

The x term is -8x.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8x + 16 + x2 = 14.22222222 + 16

Reorder the terms:
16 + -8x + x2 = 14.22222222 + 16

Combine like terms: 14.22222222 + 16 = 30.22222222
16 + -8x + x2 = 30.22222222

Factor a perfect square on the left side:
(x + -4)(x + -4) = 30.22222222

Calculate the square root of the right side: 5.497474167

Break this problem into two subproblems by setting 
(x + -4) equal to 5.497474167 and -5.497474167.

Subproblem 1

x + -4 = 5.497474167 Simplifying x + -4 = 5.497474167 Reorder the terms: -4 + x = 5.497474167 Solving -4 + x = 5.497474167 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + x = 5.497474167 + 4 Combine like terms: -4 + 4 = 0 0 + x = 5.497474167 + 4 x = 5.497474167 + 4 Combine like terms: 5.497474167 + 4 = 9.497474167 x = 9.497474167 Simplifying x = 9.497474167

Subproblem 2

x + -4 = -5.497474167 Simplifying x + -4 = -5.497474167 Reorder the terms: -4 + x = -5.497474167 Solving -4 + x = -5.497474167 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + x = -5.497474167 + 4 Combine like terms: -4 + 4 = 0 0 + x = -5.497474167 + 4 x = -5.497474167 + 4 Combine like terms: -5.497474167 + 4 = -1.497474167 x = -1.497474167 Simplifying x = -1.497474167

Solution

The solution to the problem is based on the solutions from the subproblems. x = {9.497474167, -1.497474167}

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