3x^2-1=-8x

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Solution for 3x^2-1=-8x equation:


Simplifying
3x2 + -1 = -8x

Reorder the terms:
-1 + 3x2 = -8x

Solving
-1 + 3x2 = -8x

Solving for variable 'x'.

Reorder the terms:
-1 + 8x + 3x2 = -8x + 8x

Combine like terms: -8x + 8x = 0
-1 + 8x + 3x2 = 0

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

Divide each side by '3'.
-0.3333333333 + 2.666666667x + x2 = 0

Move the constant term to the right:

Add '0.3333333333' to each side of the equation.
-0.3333333333 + 2.666666667x + 0.3333333333 + x2 = 0 + 0.3333333333

Reorder the terms:
-0.3333333333 + 0.3333333333 + 2.666666667x + x2 = 0 + 0.3333333333

Combine like terms: -0.3333333333 + 0.3333333333 = 0.0000000000
0.0000000000 + 2.666666667x + x2 = 0 + 0.3333333333
2.666666667x + x2 = 0 + 0.3333333333

Combine like terms: 0 + 0.3333333333 = 0.3333333333
2.666666667x + x2 = 0.3333333333

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 = 0.3333333333 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667x + x2 = 0.3333333333 + 1.777777780

Combine like terms: 0.3333333333 + 1.777777780 = 2.1111111133
1.777777780 + 2.666666667x + x2 = 2.1111111133

Factor a perfect square on the left side:
(x + 1.333333334)(x + 1.333333334) = 2.1111111133

Calculate the square root of the right side: 1.452966315

Break this problem into two subproblems by setting 
(x + 1.333333334) equal to 1.452966315 and -1.452966315.

Subproblem 1

x + 1.333333334 = 1.452966315 Simplifying x + 1.333333334 = 1.452966315 Reorder the terms: 1.333333334 + x = 1.452966315 Solving 1.333333334 + x = 1.452966315 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 = 1.452966315 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = 1.452966315 + -1.333333334 x = 1.452966315 + -1.333333334 Combine like terms: 1.452966315 + -1.333333334 = 0.119632981 x = 0.119632981 Simplifying x = 0.119632981

Subproblem 2

x + 1.333333334 = -1.452966315 Simplifying x + 1.333333334 = -1.452966315 Reorder the terms: 1.333333334 + x = -1.452966315 Solving 1.333333334 + x = -1.452966315 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 = -1.452966315 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = -1.452966315 + -1.333333334 x = -1.452966315 + -1.333333334 Combine like terms: -1.452966315 + -1.333333334 = -2.786299649 x = -2.786299649 Simplifying x = -2.786299649

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.119632981, -2.786299649}

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