3x^2-8x-18=0

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Solution for 3x^2-8x-18=0 equation:


Simplifying
3x2 + -8x + -18 = 0

Reorder the terms:
-18 + -8x + 3x2 = 0

Solving
-18 + -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'.
-6 + -2.666666667x + x2 = 0

Move the constant term to the right:

Add '6' to each side of the equation.
-6 + -2.666666667x + 6 + x2 = 0 + 6

Reorder the terms:
-6 + 6 + -2.666666667x + x2 = 0 + 6

Combine like terms: -6 + 6 = 0
0 + -2.666666667x + x2 = 0 + 6
-2.666666667x + x2 = 0 + 6

Combine like terms: 0 + 6 = 6
-2.666666667x + x2 = 6

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 = 6 + 1.777777780

Reorder the terms:
1.777777780 + -2.666666667x + x2 = 6 + 1.777777780

Combine like terms: 6 + 1.777777780 = 7.77777778
1.777777780 + -2.666666667x + x2 = 7.77777778

Factor a perfect square on the left side:
(x + -1.333333334)(x + -1.333333334) = 7.77777778

Calculate the square root of the right side: 2.788866756

Break this problem into two subproblems by setting 
(x + -1.333333334) equal to 2.788866756 and -2.788866756.

Subproblem 1

x + -1.333333334 = 2.788866756 Simplifying x + -1.333333334 = 2.788866756 Reorder the terms: -1.333333334 + x = 2.788866756 Solving -1.333333334 + x = 2.788866756 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 = 2.788866756 + 1.333333334 Combine like terms: -1.333333334 + 1.333333334 = 0.000000000 0.000000000 + x = 2.788866756 + 1.333333334 x = 2.788866756 + 1.333333334 Combine like terms: 2.788866756 + 1.333333334 = 4.12220009 x = 4.12220009 Simplifying x = 4.12220009

Subproblem 2

x + -1.333333334 = -2.788866756 Simplifying x + -1.333333334 = -2.788866756 Reorder the terms: -1.333333334 + x = -2.788866756 Solving -1.333333334 + x = -2.788866756 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 = -2.788866756 + 1.333333334 Combine like terms: -1.333333334 + 1.333333334 = 0.000000000 0.000000000 + x = -2.788866756 + 1.333333334 x = -2.788866756 + 1.333333334 Combine like terms: -2.788866756 + 1.333333334 = -1.455533422 x = -1.455533422 Simplifying x = -1.455533422

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.12220009, -1.455533422}

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