9x^2-8x-72=0

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Solution for 9x^2-8x-72=0 equation:


Simplifying
9x2 + -8x + -72 = 0

Reorder the terms:
-72 + -8x + 9x2 = 0

Solving
-72 + -8x + 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'.
-8 + -0.8888888889x + x2 = 0

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + -0.8888888889x + 8 + x2 = 0 + 8

Reorder the terms:
-8 + 8 + -0.8888888889x + x2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + -0.8888888889x + x2 = 0 + 8
-0.8888888889x + x2 = 0 + 8

Combine like terms: 0 + 8 = 8
-0.8888888889x + x2 = 8

The x term is -0.8888888889x.  Take half its coefficient (-0.4444444445).
Square it (0.1975308642) and add it to both sides.

Add '0.1975308642' to each side of the equation.
-0.8888888889x + 0.1975308642 + x2 = 8 + 0.1975308642

Reorder the terms:
0.1975308642 + -0.8888888889x + x2 = 8 + 0.1975308642

Combine like terms: 8 + 0.1975308642 = 8.1975308642
0.1975308642 + -0.8888888889x + x2 = 8.1975308642

Factor a perfect square on the left side:
(x + -0.4444444445)(x + -0.4444444445) = 8.1975308642

Calculate the square root of the right side: 2.86313305

Break this problem into two subproblems by setting 
(x + -0.4444444445) equal to 2.86313305 and -2.86313305.

Subproblem 1

x + -0.4444444445 = 2.86313305 Simplifying x + -0.4444444445 = 2.86313305 Reorder the terms: -0.4444444445 + x = 2.86313305 Solving -0.4444444445 + x = 2.86313305 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4444444445' to each side of the equation. -0.4444444445 + 0.4444444445 + x = 2.86313305 + 0.4444444445 Combine like terms: -0.4444444445 + 0.4444444445 = 0.0000000000 0.0000000000 + x = 2.86313305 + 0.4444444445 x = 2.86313305 + 0.4444444445 Combine like terms: 2.86313305 + 0.4444444445 = 3.3075774945 x = 3.3075774945 Simplifying x = 3.3075774945

Subproblem 2

x + -0.4444444445 = -2.86313305 Simplifying x + -0.4444444445 = -2.86313305 Reorder the terms: -0.4444444445 + x = -2.86313305 Solving -0.4444444445 + x = -2.86313305 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4444444445' to each side of the equation. -0.4444444445 + 0.4444444445 + x = -2.86313305 + 0.4444444445 Combine like terms: -0.4444444445 + 0.4444444445 = 0.0000000000 0.0000000000 + x = -2.86313305 + 0.4444444445 x = -2.86313305 + 0.4444444445 Combine like terms: -2.86313305 + 0.4444444445 = -2.4186886055 x = -2.4186886055 Simplifying x = -2.4186886055

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.3075774945, -2.4186886055}

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