0=x^2-x-9

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


Simplifying
0 = x2 + -1x + -9

Reorder the terms:
0 = -9 + -1x + x2

Solving
0 = -9 + -1x + x2

Solving for variable 'x'.

Combine like terms: 0 + 9 = 9
9 + x + -1x2 = -9 + -1x + x2 + 9 + x + -1x2

Reorder the terms:
9 + x + -1x2 = -9 + 9 + -1x + x + x2 + -1x2

Combine like terms: -9 + 9 = 0
9 + x + -1x2 = 0 + -1x + x + x2 + -1x2
9 + x + -1x2 = -1x + x + x2 + -1x2

Combine like terms: -1x + x = 0
9 + x + -1x2 = 0 + x2 + -1x2
9 + x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
9 + x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-9 + -1x + x2 = 0

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + -1x + 9 + x2 = 0 + 9

Reorder the terms:
-9 + 9 + -1x + x2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + -1x + x2 = 0 + 9
-1x + x2 = 0 + 9

Combine like terms: 0 + 9 = 9
-1x + x2 = 9

The x term is x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1x + 0.25 + x2 = 9 + 0.25

Reorder the terms:
0.25 + -1x + x2 = 9 + 0.25

Combine like terms: 9 + 0.25 = 9.25
0.25 + -1x + x2 = 9.25

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 9.25

Calculate the square root of the right side: 3.041381265

Break this problem into two subproblems by setting 
(x + 0.5) equal to 3.041381265 and -3.041381265.

Subproblem 1

x + 0.5 = 3.041381265 Simplifying x + 0.5 = 3.041381265 Reorder the terms: 0.5 + x = 3.041381265 Solving 0.5 + x = 3.041381265 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = 3.041381265 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 3.041381265 + -0.5 x = 3.041381265 + -0.5 Combine like terms: 3.041381265 + -0.5 = 2.541381265 x = 2.541381265 Simplifying x = 2.541381265

Subproblem 2

x + 0.5 = -3.041381265 Simplifying x + 0.5 = -3.041381265 Reorder the terms: 0.5 + x = -3.041381265 Solving 0.5 + x = -3.041381265 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = -3.041381265 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -3.041381265 + -0.5 x = -3.041381265 + -0.5 Combine like terms: -3.041381265 + -0.5 = -3.541381265 x = -3.541381265 Simplifying x = -3.541381265

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.541381265, -3.541381265}

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