x^2+13x=9

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Solution for x^2+13x=9 equation:


Simplifying
x2 + 13x = 9

Reorder the terms:
13x + x2 = 9

Solving
13x + x2 = 9

Solving for variable 'x'.

Reorder the terms:
-9 + 13x + x2 = 9 + -9

Combine like terms: 9 + -9 = 0
-9 + 13x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + 13x + 9 + x2 = 0 + 9

Reorder the terms:
-9 + 9 + 13x + x2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + 13x + x2 = 0 + 9
13x + x2 = 0 + 9

Combine like terms: 0 + 9 = 9
13x + x2 = 9

The x term is 13x.  Take half its coefficient (6.5).
Square it (42.25) and add it to both sides.

Add '42.25' to each side of the equation.
13x + 42.25 + x2 = 9 + 42.25

Reorder the terms:
42.25 + 13x + x2 = 9 + 42.25

Combine like terms: 9 + 42.25 = 51.25
42.25 + 13x + x2 = 51.25

Factor a perfect square on the left side:
(x + 6.5)(x + 6.5) = 51.25

Calculate the square root of the right side: 7.158910532

Break this problem into two subproblems by setting 
(x + 6.5) equal to 7.158910532 and -7.158910532.

Subproblem 1

x + 6.5 = 7.158910532 Simplifying x + 6.5 = 7.158910532 Reorder the terms: 6.5 + x = 7.158910532 Solving 6.5 + x = 7.158910532 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6.5' to each side of the equation. 6.5 + -6.5 + x = 7.158910532 + -6.5 Combine like terms: 6.5 + -6.5 = 0.0 0.0 + x = 7.158910532 + -6.5 x = 7.158910532 + -6.5 Combine like terms: 7.158910532 + -6.5 = 0.658910532 x = 0.658910532 Simplifying x = 0.658910532

Subproblem 2

x + 6.5 = -7.158910532 Simplifying x + 6.5 = -7.158910532 Reorder the terms: 6.5 + x = -7.158910532 Solving 6.5 + x = -7.158910532 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6.5' to each side of the equation. 6.5 + -6.5 + x = -7.158910532 + -6.5 Combine like terms: 6.5 + -6.5 = 0.0 0.0 + x = -7.158910532 + -6.5 x = -7.158910532 + -6.5 Combine like terms: -7.158910532 + -6.5 = -13.658910532 x = -13.658910532 Simplifying x = -13.658910532

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.658910532, -13.658910532}

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