3x^2+5x-120=0

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Solution for 3x^2+5x-120=0 equation:


Simplifying
3x2 + 5x + -120 = 0

Reorder the terms:
-120 + 5x + 3x2 = 0

Solving
-120 + 5x + 3x2 = 0

Solving for variable 'x'.

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

Divide each side by '3'.
-40 + 1.666666667x + x2 = 0

Move the constant term to the right:

Add '40' to each side of the equation.
-40 + 1.666666667x + 40 + x2 = 0 + 40

Reorder the terms:
-40 + 40 + 1.666666667x + x2 = 0 + 40

Combine like terms: -40 + 40 = 0
0 + 1.666666667x + x2 = 0 + 40
1.666666667x + x2 = 0 + 40

Combine like terms: 0 + 40 = 40
1.666666667x + x2 = 40

The x term is 1.666666667x.  Take half its coefficient (0.8333333335).
Square it (0.6944444447) and add it to both sides.

Add '0.6944444447' to each side of the equation.
1.666666667x + 0.6944444447 + x2 = 40 + 0.6944444447

Reorder the terms:
0.6944444447 + 1.666666667x + x2 = 40 + 0.6944444447

Combine like terms: 40 + 0.6944444447 = 40.6944444447
0.6944444447 + 1.666666667x + x2 = 40.6944444447

Factor a perfect square on the left side:
(x + 0.8333333335)(x + 0.8333333335) = 40.6944444447

Calculate the square root of the right side: 6.379219736

Break this problem into two subproblems by setting 
(x + 0.8333333335) equal to 6.379219736 and -6.379219736.

Subproblem 1

x + 0.8333333335 = 6.379219736 Simplifying x + 0.8333333335 = 6.379219736 Reorder the terms: 0.8333333335 + x = 6.379219736 Solving 0.8333333335 + x = 6.379219736 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + x = 6.379219736 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + x = 6.379219736 + -0.8333333335 x = 6.379219736 + -0.8333333335 Combine like terms: 6.379219736 + -0.8333333335 = 5.5458864025 x = 5.5458864025 Simplifying x = 5.5458864025

Subproblem 2

x + 0.8333333335 = -6.379219736 Simplifying x + 0.8333333335 = -6.379219736 Reorder the terms: 0.8333333335 + x = -6.379219736 Solving 0.8333333335 + x = -6.379219736 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.8333333335' to each side of the equation. 0.8333333335 + -0.8333333335 + x = -6.379219736 + -0.8333333335 Combine like terms: 0.8333333335 + -0.8333333335 = 0.0000000000 0.0000000000 + x = -6.379219736 + -0.8333333335 x = -6.379219736 + -0.8333333335 Combine like terms: -6.379219736 + -0.8333333335 = -7.2125530695 x = -7.2125530695 Simplifying x = -7.2125530695

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.5458864025, -7.2125530695}

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