15x^2-4x-12=0

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Solution for 15x^2-4x-12=0 equation: 


Simplifying
15x2 + -4x + -12 = 0

Reorder the terms:
-12 + -4x + 15x2 = 0

Solving
-12 + -4x + 15x2 = 0

Solving for variable 'x'.

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

Divide each side by '15'.
-0.8 + -0.2666666667x + x2 = 0

Move the constant term to the right:

Add '0.8' to each side of the equation.
-0.8 + -0.2666666667x + 0.8 + x2 = 0 + 0.8

Reorder the terms:
-0.8 + 0.8 + -0.2666666667x + x2 = 0 + 0.8

Combine like terms: -0.8 + 0.8 = 0.0
0.0 + -0.2666666667x + x2 = 0 + 0.8
-0.2666666667x + x2 = 0 + 0.8

Combine like terms: 0 + 0.8 = 0.8
-0.2666666667x + x2 = 0.8

The x term is -0.2666666667x.  Take half its coefficient (-0.1333333334).
Square it (0.01777777780) and add it to both sides.

Add '0.01777777780' to each side of the equation.
-0.2666666667x + 0.01777777780 + x2 = 0.8 + 0.01777777780

Reorder the terms:
0.01777777780 + -0.2666666667x + x2 = 0.8 + 0.01777777780

Combine like terms: 0.8 + 0.01777777780 = 0.8177777778
0.01777777780 + -0.2666666667x + x2 = 0.8177777778

Factor a perfect square on the left side:
(x + -0.1333333334)(x + -0.1333333334) = 0.8177777778

Calculate the square root of the right side: 0.904310664

Break this problem into two subproblems by setting 
(x + -0.1333333334) equal to 0.904310664 and -0.904310664.


Subproblem 1
x + -0.1333333334 = 0.904310664

Simplifying
x + -0.1333333334 = 0.904310664

Reorder the terms:
-0.1333333334 + x = 0.904310664

Solving
-0.1333333334 + x = 0.904310664

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '0.1333333334' to each side of the equation.
-0.1333333334 + 0.1333333334 + x = 0.904310664 + 0.1333333334

Combine like terms: -0.1333333334 + 0.1333333334 = 0.0000000000
0.0000000000 + x = 0.904310664 + 0.1333333334
x = 0.904310664 + 0.1333333334

Combine like terms: 0.904310664 + 0.1333333334 = 1.0376439974
x = 1.0376439974

Simplifying
x = 1.0376439974


Subproblem 2
x + -0.1333333334 = -0.904310664

Simplifying
x + -0.1333333334 = -0.904310664

Reorder the terms:
-0.1333333334 + x = -0.904310664

Solving
-0.1333333334 + x = -0.904310664

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '0.1333333334' to each side of the equation.
-0.1333333334 + 0.1333333334 + x = -0.904310664 + 0.1333333334

Combine like terms: -0.1333333334 + 0.1333333334 = 0.0000000000
0.0000000000 + x = -0.904310664 + 0.1333333334
x = -0.904310664 + 0.1333333334

Combine like terms: -0.904310664 + 0.1333333334 = -0.7709773306
x = -0.7709773306

Simplifying
x = -0.7709773306


Solution
The solution to the problem is based on the solutions
from the subproblems.
x = {1.0376439974, -0.7709773306}

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