x^2-31x-84=0

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Solution for x^2-31x-84=0 equation:


Simplifying
x2 + -31x + -84 = 0

Reorder the terms:
-84 + -31x + x2 = 0

Solving
-84 + -31x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '84' to each side of the equation.
-84 + -31x + 84 + x2 = 0 + 84

Reorder the terms:
-84 + 84 + -31x + x2 = 0 + 84

Combine like terms: -84 + 84 = 0
0 + -31x + x2 = 0 + 84
-31x + x2 = 0 + 84

Combine like terms: 0 + 84 = 84
-31x + x2 = 84

The x term is -31x.  Take half its coefficient (-15.5).
Square it (240.25) and add it to both sides.

Add '240.25' to each side of the equation.
-31x + 240.25 + x2 = 84 + 240.25

Reorder the terms:
240.25 + -31x + x2 = 84 + 240.25

Combine like terms: 84 + 240.25 = 324.25
240.25 + -31x + x2 = 324.25

Factor a perfect square on the left side:
(x + -15.5)(x + -15.5) = 324.25

Calculate the square root of the right side: 18.006943105

Break this problem into two subproblems by setting 
(x + -15.5) equal to 18.006943105 and -18.006943105.

Subproblem 1

x + -15.5 = 18.006943105 Simplifying x + -15.5 = 18.006943105 Reorder the terms: -15.5 + x = 18.006943105 Solving -15.5 + x = 18.006943105 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '15.5' to each side of the equation. -15.5 + 15.5 + x = 18.006943105 + 15.5 Combine like terms: -15.5 + 15.5 = 0.0 0.0 + x = 18.006943105 + 15.5 x = 18.006943105 + 15.5 Combine like terms: 18.006943105 + 15.5 = 33.506943105 x = 33.506943105 Simplifying x = 33.506943105

Subproblem 2

x + -15.5 = -18.006943105 Simplifying x + -15.5 = -18.006943105 Reorder the terms: -15.5 + x = -18.006943105 Solving -15.5 + x = -18.006943105 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '15.5' to each side of the equation. -15.5 + 15.5 + x = -18.006943105 + 15.5 Combine like terms: -15.5 + 15.5 = 0.0 0.0 + x = -18.006943105 + 15.5 x = -18.006943105 + 15.5 Combine like terms: -18.006943105 + 15.5 = -2.506943105 x = -2.506943105 Simplifying x = -2.506943105

Solution

The solution to the problem is based on the solutions from the subproblems. x = {33.506943105, -2.506943105}

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