3x^2-x-120=0

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


Simplifying
3x2 + -1x + -120 = 0

Reorder the terms:
-120 + -1x + 3x2 = 0

Solving
-120 + -1x + 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 + -0.3333333333x + x2 = 0

Move the constant term to the right:

Add '40' to each side of the equation.
-40 + -0.3333333333x + 40 + x2 = 0 + 40

Reorder the terms:
-40 + 40 + -0.3333333333x + x2 = 0 + 40

Combine like terms: -40 + 40 = 0
0 + -0.3333333333x + x2 = 0 + 40
-0.3333333333x + x2 = 0 + 40

Combine like terms: 0 + 40 = 40
-0.3333333333x + x2 = 40

The x term is -0.3333333333x.  Take half its coefficient (-0.1666666667).
Square it (0.02777777779) and add it to both sides.

Add '0.02777777779' to each side of the equation.
-0.3333333333x + 0.02777777779 + x2 = 40 + 0.02777777779

Reorder the terms:
0.02777777779 + -0.3333333333x + x2 = 40 + 0.02777777779

Combine like terms: 40 + 0.02777777779 = 40.02777777779
0.02777777779 + -0.3333333333x + x2 = 40.02777777779

Factor a perfect square on the left side:
(x + -0.1666666667)(x + -0.1666666667) = 40.02777777779

Calculate the square root of the right side: 6.326750965

Break this problem into two subproblems by setting 
(x + -0.1666666667) equal to 6.326750965 and -6.326750965.

Subproblem 1

x + -0.1666666667 = 6.326750965 Simplifying x + -0.1666666667 = 6.326750965 Reorder the terms: -0.1666666667 + x = 6.326750965 Solving -0.1666666667 + x = 6.326750965 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.1666666667' to each side of the equation. -0.1666666667 + 0.1666666667 + x = 6.326750965 + 0.1666666667 Combine like terms: -0.1666666667 + 0.1666666667 = 0.0000000000 0.0000000000 + x = 6.326750965 + 0.1666666667 x = 6.326750965 + 0.1666666667 Combine like terms: 6.326750965 + 0.1666666667 = 6.4934176317 x = 6.4934176317 Simplifying x = 6.4934176317

Subproblem 2

x + -0.1666666667 = -6.326750965 Simplifying x + -0.1666666667 = -6.326750965 Reorder the terms: -0.1666666667 + x = -6.326750965 Solving -0.1666666667 + x = -6.326750965 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.1666666667' to each side of the equation. -0.1666666667 + 0.1666666667 + x = -6.326750965 + 0.1666666667 Combine like terms: -0.1666666667 + 0.1666666667 = 0.0000000000 0.0000000000 + x = -6.326750965 + 0.1666666667 x = -6.326750965 + 0.1666666667 Combine like terms: -6.326750965 + 0.1666666667 = -6.1600842983 x = -6.1600842983 Simplifying x = -6.1600842983

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.4934176317, -6.1600842983}

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