x^2+9x=123

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Solution for x^2+9x=123 equation:


Simplifying
x2 + 9x = 123

Reorder the terms:
9x + x2 = 123

Solving
9x + x2 = 123

Solving for variable 'x'.

Reorder the terms:
-123 + 9x + x2 = 123 + -123

Combine like terms: 123 + -123 = 0
-123 + 9x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '123' to each side of the equation.
-123 + 9x + 123 + x2 = 0 + 123

Reorder the terms:
-123 + 123 + 9x + x2 = 0 + 123

Combine like terms: -123 + 123 = 0
0 + 9x + x2 = 0 + 123
9x + x2 = 0 + 123

Combine like terms: 0 + 123 = 123
9x + x2 = 123

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 = 123 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 123 + 20.25

Combine like terms: 123 + 20.25 = 143.25
20.25 + 9x + x2 = 143.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 143.25

Calculate the square root of the right side: 11.968709204

Break this problem into two subproblems by setting 
(x + 4.5) equal to 11.968709204 and -11.968709204.

Subproblem 1

x + 4.5 = 11.968709204 Simplifying x + 4.5 = 11.968709204 Reorder the terms: 4.5 + x = 11.968709204 Solving 4.5 + x = 11.968709204 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 = 11.968709204 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 11.968709204 + -4.5 x = 11.968709204 + -4.5 Combine like terms: 11.968709204 + -4.5 = 7.468709204 x = 7.468709204 Simplifying x = 7.468709204

Subproblem 2

x + 4.5 = -11.968709204 Simplifying x + 4.5 = -11.968709204 Reorder the terms: 4.5 + x = -11.968709204 Solving 4.5 + x = -11.968709204 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 = -11.968709204 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -11.968709204 + -4.5 x = -11.968709204 + -4.5 Combine like terms: -11.968709204 + -4.5 = -16.468709204 x = -16.468709204 Simplifying x = -16.468709204

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.468709204, -16.468709204}

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