x(9+2x)=120

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Solution for x(9+2x)=120 equation:


Simplifying
x(9 + 2x) = 120
(9 * x + 2x * x) = 120
(9x + 2x2) = 120

Solving
9x + 2x2 = 120

Solving for variable 'x'.

Reorder the terms:
-120 + 9x + 2x2 = 120 + -120

Combine like terms: 120 + -120 = 0
-120 + 9x + 2x2 = 0

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

Divide each side by '2'.
-60 + 4.5x + x2 = 0

Move the constant term to the right:

Add '60' to each side of the equation.
-60 + 4.5x + 60 + x2 = 0 + 60

Reorder the terms:
-60 + 60 + 4.5x + x2 = 0 + 60

Combine like terms: -60 + 60 = 0
0 + 4.5x + x2 = 0 + 60
4.5x + x2 = 0 + 60

Combine like terms: 0 + 60 = 60
4.5x + x2 = 60

The x term is 4.5x.  Take half its coefficient (2.25).
Square it (5.0625) and add it to both sides.

Add '5.0625' to each side of the equation.
4.5x + 5.0625 + x2 = 60 + 5.0625

Reorder the terms:
5.0625 + 4.5x + x2 = 60 + 5.0625

Combine like terms: 60 + 5.0625 = 65.0625
5.0625 + 4.5x + x2 = 65.0625

Factor a perfect square on the left side:
(x + 2.25)(x + 2.25) = 65.0625

Calculate the square root of the right side: 8.066132902

Break this problem into two subproblems by setting 
(x + 2.25) equal to 8.066132902 and -8.066132902.

Subproblem 1

x + 2.25 = 8.066132902 Simplifying x + 2.25 = 8.066132902 Reorder the terms: 2.25 + x = 8.066132902 Solving 2.25 + x = 8.066132902 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.25' to each side of the equation. 2.25 + -2.25 + x = 8.066132902 + -2.25 Combine like terms: 2.25 + -2.25 = 0.00 0.00 + x = 8.066132902 + -2.25 x = 8.066132902 + -2.25 Combine like terms: 8.066132902 + -2.25 = 5.816132902 x = 5.816132902 Simplifying x = 5.816132902

Subproblem 2

x + 2.25 = -8.066132902 Simplifying x + 2.25 = -8.066132902 Reorder the terms: 2.25 + x = -8.066132902 Solving 2.25 + x = -8.066132902 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.25' to each side of the equation. 2.25 + -2.25 + x = -8.066132902 + -2.25 Combine like terms: 2.25 + -2.25 = 0.00 0.00 + x = -8.066132902 + -2.25 x = -8.066132902 + -2.25 Combine like terms: -8.066132902 + -2.25 = -10.316132902 x = -10.316132902 Simplifying x = -10.316132902

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.816132902, -10.316132902}

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