15=x^2+9x

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Solution for 15=x^2+9x equation:


Simplifying
15 = x2 + 9x

Reorder the terms:
15 = 9x + x2

Solving
15 = 9x + x2

Solving for variable 'x'.

Reorder the terms:
15 + -9x + -1x2 = 9x + -9x + x2 + -1x2

Combine like terms: 9x + -9x = 0
15 + -9x + -1x2 = 0 + x2 + -1x2
15 + -9x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
15 + -9x + -1x2 = 0

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

Divide each side by '-1'.
-15 + 9x + x2 = 0

Move the constant term to the right:

Add '15' to each side of the equation.
-15 + 9x + 15 + x2 = 0 + 15

Reorder the terms:
-15 + 15 + 9x + x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + 9x + x2 = 0 + 15
9x + x2 = 0 + 15

Combine like terms: 0 + 15 = 15
9x + x2 = 15

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 = 15 + 20.25

Reorder the terms:
20.25 + 9x + x2 = 15 + 20.25

Combine like terms: 15 + 20.25 = 35.25
20.25 + 9x + x2 = 35.25

Factor a perfect square on the left side:
(x + 4.5)(x + 4.5) = 35.25

Calculate the square root of the right side: 5.937171044

Break this problem into two subproblems by setting 
(x + 4.5) equal to 5.937171044 and -5.937171044.

Subproblem 1

x + 4.5 = 5.937171044 Simplifying x + 4.5 = 5.937171044 Reorder the terms: 4.5 + x = 5.937171044 Solving 4.5 + x = 5.937171044 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 = 5.937171044 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = 5.937171044 + -4.5 x = 5.937171044 + -4.5 Combine like terms: 5.937171044 + -4.5 = 1.437171044 x = 1.437171044 Simplifying x = 1.437171044

Subproblem 2

x + 4.5 = -5.937171044 Simplifying x + 4.5 = -5.937171044 Reorder the terms: 4.5 + x = -5.937171044 Solving 4.5 + x = -5.937171044 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 = -5.937171044 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x = -5.937171044 + -4.5 x = -5.937171044 + -4.5 Combine like terms: -5.937171044 + -4.5 = -10.437171044 x = -10.437171044 Simplifying x = -10.437171044

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.437171044, -10.437171044}

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