3x^2+8x-138=0

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Solution for 3x^2+8x-138=0 equation:


Simplifying
3x2 + 8x + -138 = 0

Reorder the terms:
-138 + 8x + 3x2 = 0

Solving
-138 + 8x + 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'.
-46 + 2.666666667x + x2 = 0

Move the constant term to the right:

Add '46' to each side of the equation.
-46 + 2.666666667x + 46 + x2 = 0 + 46

Reorder the terms:
-46 + 46 + 2.666666667x + x2 = 0 + 46

Combine like terms: -46 + 46 = 0
0 + 2.666666667x + x2 = 0 + 46
2.666666667x + x2 = 0 + 46

Combine like terms: 0 + 46 = 46
2.666666667x + x2 = 46

The x term is 2.666666667x.  Take half its coefficient (1.333333334).
Square it (1.777777780) and add it to both sides.

Add '1.777777780' to each side of the equation.
2.666666667x + 1.777777780 + x2 = 46 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667x + x2 = 46 + 1.777777780

Combine like terms: 46 + 1.777777780 = 47.77777778
1.777777780 + 2.666666667x + x2 = 47.77777778

Factor a perfect square on the left side:
(x + 1.333333334)(x + 1.333333334) = 47.77777778

Calculate the square root of the right side: 6.912147118

Break this problem into two subproblems by setting 
(x + 1.333333334) equal to 6.912147118 and -6.912147118.

Subproblem 1

x + 1.333333334 = 6.912147118 Simplifying x + 1.333333334 = 6.912147118 Reorder the terms: 1.333333334 + x = 6.912147118 Solving 1.333333334 + x = 6.912147118 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.333333334' to each side of the equation. 1.333333334 + -1.333333334 + x = 6.912147118 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = 6.912147118 + -1.333333334 x = 6.912147118 + -1.333333334 Combine like terms: 6.912147118 + -1.333333334 = 5.578813784 x = 5.578813784 Simplifying x = 5.578813784

Subproblem 2

x + 1.333333334 = -6.912147118 Simplifying x + 1.333333334 = -6.912147118 Reorder the terms: 1.333333334 + x = -6.912147118 Solving 1.333333334 + x = -6.912147118 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.333333334' to each side of the equation. 1.333333334 + -1.333333334 + x = -6.912147118 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = -6.912147118 + -1.333333334 x = -6.912147118 + -1.333333334 Combine like terms: -6.912147118 + -1.333333334 = -8.245480452 x = -8.245480452 Simplifying x = -8.245480452

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.578813784, -8.245480452}

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