3x^2+8x-56=0

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Solution for 3x^2+8x-56=0 equation:


Simplifying
3x2 + 8x + -56 = 0

Reorder the terms:
-56 + 8x + 3x2 = 0

Solving
-56 + 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'.
-18.66666667 + 2.666666667x + x2 = 0

Move the constant term to the right:

Add '18.66666667' to each side of the equation.
-18.66666667 + 2.666666667x + 18.66666667 + x2 = 0 + 18.66666667

Reorder the terms:
-18.66666667 + 18.66666667 + 2.666666667x + x2 = 0 + 18.66666667

Combine like terms: -18.66666667 + 18.66666667 = 0.00000000
0.00000000 + 2.666666667x + x2 = 0 + 18.66666667
2.666666667x + x2 = 0 + 18.66666667

Combine like terms: 0 + 18.66666667 = 18.66666667
2.666666667x + x2 = 18.66666667

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 = 18.66666667 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667x + x2 = 18.66666667 + 1.777777780

Combine like terms: 18.66666667 + 1.777777780 = 20.44444445
1.777777780 + 2.666666667x + x2 = 20.44444445

Factor a perfect square on the left side:
(x + 1.333333334)(x + 1.333333334) = 20.44444445

Calculate the square root of the right side: 4.521553323

Break this problem into two subproblems by setting 
(x + 1.333333334) equal to 4.521553323 and -4.521553323.

Subproblem 1

x + 1.333333334 = 4.521553323 Simplifying x + 1.333333334 = 4.521553323 Reorder the terms: 1.333333334 + x = 4.521553323 Solving 1.333333334 + x = 4.521553323 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 = 4.521553323 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = 4.521553323 + -1.333333334 x = 4.521553323 + -1.333333334 Combine like terms: 4.521553323 + -1.333333334 = 3.188219989 x = 3.188219989 Simplifying x = 3.188219989

Subproblem 2

x + 1.333333334 = -4.521553323 Simplifying x + 1.333333334 = -4.521553323 Reorder the terms: 1.333333334 + x = -4.521553323 Solving 1.333333334 + x = -4.521553323 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 = -4.521553323 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = -4.521553323 + -1.333333334 x = -4.521553323 + -1.333333334 Combine like terms: -4.521553323 + -1.333333334 = -5.854886657 x = -5.854886657 Simplifying x = -5.854886657

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.188219989, -5.854886657}

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