x^2-13x-72=0

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Solution for x^2-13x-72=0 equation:


Simplifying
x2 + -13x + -72 = 0

Reorder the terms:
-72 + -13x + x2 = 0

Solving
-72 + -13x + 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 + -13x + 72 + x2 = 0 + 72

Reorder the terms:
-72 + 72 + -13x + x2 = 0 + 72

Combine like terms: -72 + 72 = 0
0 + -13x + x2 = 0 + 72
-13x + x2 = 0 + 72

Combine like terms: 0 + 72 = 72
-13x + x2 = 72

The x term is -13x.  Take half its coefficient (-6.5).
Square it (42.25) and add it to both sides.

Add '42.25' to each side of the equation.
-13x + 42.25 + x2 = 72 + 42.25

Reorder the terms:
42.25 + -13x + x2 = 72 + 42.25

Combine like terms: 72 + 42.25 = 114.25
42.25 + -13x + x2 = 114.25

Factor a perfect square on the left side:
(x + -6.5)(x + -6.5) = 114.25

Calculate the square root of the right side: 10.688779163

Break this problem into two subproblems by setting 
(x + -6.5) equal to 10.688779163 and -10.688779163.

Subproblem 1

x + -6.5 = 10.688779163 Simplifying x + -6.5 = 10.688779163 Reorder the terms: -6.5 + x = 10.688779163 Solving -6.5 + x = 10.688779163 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '6.5' to each side of the equation. -6.5 + 6.5 + x = 10.688779163 + 6.5 Combine like terms: -6.5 + 6.5 = 0.0 0.0 + x = 10.688779163 + 6.5 x = 10.688779163 + 6.5 Combine like terms: 10.688779163 + 6.5 = 17.188779163 x = 17.188779163 Simplifying x = 17.188779163

Subproblem 2

x + -6.5 = -10.688779163 Simplifying x + -6.5 = -10.688779163 Reorder the terms: -6.5 + x = -10.688779163 Solving -6.5 + x = -10.688779163 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '6.5' to each side of the equation. -6.5 + 6.5 + x = -10.688779163 + 6.5 Combine like terms: -6.5 + 6.5 = 0.0 0.0 + x = -10.688779163 + 6.5 x = -10.688779163 + 6.5 Combine like terms: -10.688779163 + 6.5 = -4.188779163 x = -4.188779163 Simplifying x = -4.188779163

Solution

The solution to the problem is based on the solutions from the subproblems. x = {17.188779163, -4.188779163}

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