3x^2+8x-12=7

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Solution for 3x^2+8x-12=7 equation:


Simplifying
3x2 + 8x + -12 = 7

Reorder the terms:
-12 + 8x + 3x2 = 7

Solving
-12 + 8x + 3x2 = 7

Solving for variable 'x'.

Reorder the terms:
-12 + -7 + 8x + 3x2 = 7 + -7

Combine like terms: -12 + -7 = -19
-19 + 8x + 3x2 = 7 + -7

Combine like terms: 7 + -7 = 0
-19 + 8x + 3x2 = 0

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

Divide each side by '3'.
-6.333333333 + 2.666666667x + x2 = 0

Move the constant term to the right:

Add '6.333333333' to each side of the equation.
-6.333333333 + 2.666666667x + 6.333333333 + x2 = 0 + 6.333333333

Reorder the terms:
-6.333333333 + 6.333333333 + 2.666666667x + x2 = 0 + 6.333333333

Combine like terms: -6.333333333 + 6.333333333 = 0.000000000
0.000000000 + 2.666666667x + x2 = 0 + 6.333333333
2.666666667x + x2 = 0 + 6.333333333

Combine like terms: 0 + 6.333333333 = 6.333333333
2.666666667x + x2 = 6.333333333

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 = 6.333333333 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667x + x2 = 6.333333333 + 1.777777780

Combine like terms: 6.333333333 + 1.777777780 = 8.111111113
1.777777780 + 2.666666667x + x2 = 8.111111113

Factor a perfect square on the left side:
(x + 1.333333334)(x + 1.333333334) = 8.111111113

Calculate the square root of the right side: 2.848001249

Break this problem into two subproblems by setting 
(x + 1.333333334) equal to 2.848001249 and -2.848001249.

Subproblem 1

x + 1.333333334 = 2.848001249 Simplifying x + 1.333333334 = 2.848001249 Reorder the terms: 1.333333334 + x = 2.848001249 Solving 1.333333334 + x = 2.848001249 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 = 2.848001249 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = 2.848001249 + -1.333333334 x = 2.848001249 + -1.333333334 Combine like terms: 2.848001249 + -1.333333334 = 1.514667915 x = 1.514667915 Simplifying x = 1.514667915

Subproblem 2

x + 1.333333334 = -2.848001249 Simplifying x + 1.333333334 = -2.848001249 Reorder the terms: 1.333333334 + x = -2.848001249 Solving 1.333333334 + x = -2.848001249 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 = -2.848001249 + -1.333333334 Combine like terms: 1.333333334 + -1.333333334 = 0.000000000 0.000000000 + x = -2.848001249 + -1.333333334 x = -2.848001249 + -1.333333334 Combine like terms: -2.848001249 + -1.333333334 = -4.181334583 x = -4.181334583 Simplifying x = -4.181334583

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.514667915, -4.181334583}

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