x^2-3x-72=0

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Solution for x^2-3x-72=0 equation:


Simplifying
x2 + -3x + -72 = 0

Reorder the terms:
-72 + -3x + x2 = 0

Solving
-72 + -3x + 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 + -3x + 72 + x2 = 0 + 72

Reorder the terms:
-72 + 72 + -3x + x2 = 0 + 72

Combine like terms: -72 + 72 = 0
0 + -3x + x2 = 0 + 72
-3x + x2 = 0 + 72

Combine like terms: 0 + 72 = 72
-3x + x2 = 72

The x term is -3x.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3x + 2.25 + x2 = 72 + 2.25

Reorder the terms:
2.25 + -3x + x2 = 72 + 2.25

Combine like terms: 72 + 2.25 = 74.25
2.25 + -3x + x2 = 74.25

Factor a perfect square on the left side:
(x + -1.5)(x + -1.5) = 74.25

Calculate the square root of the right side: 8.61684397

Break this problem into two subproblems by setting 
(x + -1.5) equal to 8.61684397 and -8.61684397.

Subproblem 1

x + -1.5 = 8.61684397 Simplifying x + -1.5 = 8.61684397 Reorder the terms: -1.5 + x = 8.61684397 Solving -1.5 + x = 8.61684397 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x = 8.61684397 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = 8.61684397 + 1.5 x = 8.61684397 + 1.5 Combine like terms: 8.61684397 + 1.5 = 10.11684397 x = 10.11684397 Simplifying x = 10.11684397

Subproblem 2

x + -1.5 = -8.61684397 Simplifying x + -1.5 = -8.61684397 Reorder the terms: -1.5 + x = -8.61684397 Solving -1.5 + x = -8.61684397 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x = -8.61684397 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = -8.61684397 + 1.5 x = -8.61684397 + 1.5 Combine like terms: -8.61684397 + 1.5 = -7.11684397 x = -7.11684397 Simplifying x = -7.11684397

Solution

The solution to the problem is based on the solutions from the subproblems. x = {10.11684397, -7.11684397}

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