16x^2-72x=81

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Solution for 16x^2-72x=81 equation:


Simplifying
16x2 + -72x = 81

Reorder the terms:
-72x + 16x2 = 81

Solving
-72x + 16x2 = 81

Solving for variable 'x'.

Reorder the terms:
-81 + -72x + 16x2 = 81 + -81

Combine like terms: 81 + -81 = 0
-81 + -72x + 16x2 = 0

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

Divide each side by '16'.
-5.0625 + -4.5x + x2 = 0

Move the constant term to the right:

Add '5.0625' to each side of the equation.
-5.0625 + -4.5x + 5.0625 + x2 = 0 + 5.0625

Reorder the terms:
-5.0625 + 5.0625 + -4.5x + x2 = 0 + 5.0625

Combine like terms: -5.0625 + 5.0625 = 0.0000
0.0000 + -4.5x + x2 = 0 + 5.0625
-4.5x + x2 = 0 + 5.0625

Combine like terms: 0 + 5.0625 = 5.0625
-4.5x + x2 = 5.0625

The x term is -4.5x.  Take half its coefficient (-2.25).
Square it (5.0625) and add it to both sides.

Add '5.0625' to each side of the equation.
-4.5x + 5.0625 + x2 = 5.0625 + 5.0625

Reorder the terms:
5.0625 + -4.5x + x2 = 5.0625 + 5.0625

Combine like terms: 5.0625 + 5.0625 = 10.125
5.0625 + -4.5x + x2 = 10.125

Factor a perfect square on the left side:
(x + -2.25)(x + -2.25) = 10.125

Calculate the square root of the right side: 3.181980515

Break this problem into two subproblems by setting 
(x + -2.25) equal to 3.181980515 and -3.181980515.

Subproblem 1

x + -2.25 = 3.181980515 Simplifying x + -2.25 = 3.181980515 Reorder the terms: -2.25 + x = 3.181980515 Solving -2.25 + x = 3.181980515 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + x = 3.181980515 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + x = 3.181980515 + 2.25 x = 3.181980515 + 2.25 Combine like terms: 3.181980515 + 2.25 = 5.431980515 x = 5.431980515 Simplifying x = 5.431980515

Subproblem 2

x + -2.25 = -3.181980515 Simplifying x + -2.25 = -3.181980515 Reorder the terms: -2.25 + x = -3.181980515 Solving -2.25 + x = -3.181980515 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + x = -3.181980515 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + x = -3.181980515 + 2.25 x = -3.181980515 + 2.25 Combine like terms: -3.181980515 + 2.25 = -0.931980515 x = -0.931980515 Simplifying x = -0.931980515

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.431980515, -0.931980515}

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