x^2-4x-72=0

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Solution for x^2-4x-72=0 equation:


Simplifying
x2 + -4x + -72 = 0

Reorder the terms:
-72 + -4x + x2 = 0

Solving
-72 + -4x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '72' to each side of the equation.
-72 + -4x + 72 + x2 = 0 + 72

Reorder the terms:
-72 + 72 + -4x + x2 = 0 + 72

Combine like terms: -72 + 72 = 0
0 + -4x + x2 = 0 + 72
-4x + x2 = 0 + 72

Combine like terms: 0 + 72 = 72
-4x + x2 = 72

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = 72 + 4

Reorder the terms:
4 + -4x + x2 = 72 + 4

Combine like terms: 72 + 4 = 76
4 + -4x + x2 = 76

Factor a perfect square on the left side:
(x + -2)(x + -2) = 76

Calculate the square root of the right side: 8.717797887

Break this problem into two subproblems by setting 
(x + -2) equal to 8.717797887 and -8.717797887.

Subproblem 1

x + -2 = 8.717797887 Simplifying x + -2 = 8.717797887 Reorder the terms: -2 + x = 8.717797887 Solving -2 + x = 8.717797887 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = 8.717797887 + 2 Combine like terms: -2 + 2 = 0 0 + x = 8.717797887 + 2 x = 8.717797887 + 2 Combine like terms: 8.717797887 + 2 = 10.717797887 x = 10.717797887 Simplifying x = 10.717797887

Subproblem 2

x + -2 = -8.717797887 Simplifying x + -2 = -8.717797887 Reorder the terms: -2 + x = -8.717797887 Solving -2 + x = -8.717797887 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = -8.717797887 + 2 Combine like terms: -2 + 2 = 0 0 + x = -8.717797887 + 2 x = -8.717797887 + 2 Combine like terms: -8.717797887 + 2 = -6.717797887 x = -6.717797887 Simplifying x = -6.717797887

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.717797887, -6.717797887}

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