x^2+9x-31=0

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Solution for x^2+9x-31=0 equation:


Simplifying
x2 + 9x + -31 = 0

Reorder the terms:
-31 + 9x + x2 = 0

Solving
-31 + 9x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '31' to each side of the equation.
-31 + 9x + 31 + x2 = 0 + 31

Reorder the terms:
-31 + 31 + 9x + x2 = 0 + 31

Combine like terms: -31 + 31 = 0
0 + 9x + x2 = 0 + 31
9x + x2 = 0 + 31

Combine like terms: 0 + 31 = 31
9x + x2 = 31

The x term is 9x.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9x + 20.25 + x2 = 31 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 31 + 20.25

Combine like terms: 31 + 20.25 = 51.25
20.25 + 9x + x2 = 51.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 51.25

Calculate the square root of the right side: 7.158910532

Break this problem into two subproblems by setting 
(x + 4.5) equal to 7.158910532 and -7.158910532.

Subproblem 1

x + 4.5 = 7.158910532 Simplifying x + 4.5 = 7.158910532 Reorder the terms: 4.5 + x = 7.158910532 Solving 4.5 + x = 7.158910532 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = 7.158910532 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 7.158910532 + -4.5 x = 7.158910532 + -4.5 Combine like terms: 7.158910532 + -4.5 = 2.658910532 x = 2.658910532 Simplifying x = 2.658910532

Subproblem 2

x + 4.5 = -7.158910532 Simplifying x + 4.5 = -7.158910532 Reorder the terms: 4.5 + x = -7.158910532 Solving 4.5 + x = -7.158910532 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x = -7.158910532 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -7.158910532 + -4.5 x = -7.158910532 + -4.5 Combine like terms: -7.158910532 + -4.5 = -11.658910532 x = -11.658910532 Simplifying x = -11.658910532

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.658910532, -11.658910532}

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