15x^2-28x-12=0

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Solution for 15x^2-28x-12=0 equation:


Simplifying
15x2 + -28x + -12 = 0

Reorder the terms:
-12 + -28x + 15x2 = 0

Solving
-12 + -28x + 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 + -1.866666667x + x2 = 0

Move the constant term to the right:

Add '0.8' to each side of the equation.
-0.8 + -1.866666667x + 0.8 + x2 = 0 + 0.8

Reorder the terms:
-0.8 + 0.8 + -1.866666667x + x2 = 0 + 0.8

Combine like terms: -0.8 + 0.8 = 0.0
0.0 + -1.866666667x + x2 = 0 + 0.8
-1.866666667x + x2 = 0 + 0.8

Combine like terms: 0 + 0.8 = 0.8
-1.866666667x + x2 = 0.8

The x term is -1.866666667x.  Take half its coefficient (-0.9333333335).
Square it (0.8711111114) and add it to both sides.

Add '0.8711111114' to each side of the equation.
-1.866666667x + 0.8711111114 + x2 = 0.8 + 0.8711111114

Reorder the terms:
0.8711111114 + -1.866666667x + x2 = 0.8 + 0.8711111114

Combine like terms: 0.8 + 0.8711111114 = 1.6711111114
0.8711111114 + -1.866666667x + x2 = 1.6711111114

Factor a perfect square on the left side:
(x + -0.9333333335)(x + -0.9333333335) = 1.6711111114

Calculate the square root of the right side: 1.292714629

Break this problem into two subproblems by setting 
(x + -0.9333333335) equal to 1.292714629 and -1.292714629.

Subproblem 1

x + -0.9333333335 = 1.292714629 Simplifying x + -0.9333333335 = 1.292714629 Reorder the terms: -0.9333333335 + x = 1.292714629 Solving -0.9333333335 + x = 1.292714629 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.9333333335' to each side of the equation. -0.9333333335 + 0.9333333335 + x = 1.292714629 + 0.9333333335 Combine like terms: -0.9333333335 + 0.9333333335 = 0.0000000000 0.0000000000 + x = 1.292714629 + 0.9333333335 x = 1.292714629 + 0.9333333335 Combine like terms: 1.292714629 + 0.9333333335 = 2.2260479625 x = 2.2260479625 Simplifying x = 2.2260479625

Subproblem 2

x + -0.9333333335 = -1.292714629 Simplifying x + -0.9333333335 = -1.292714629 Reorder the terms: -0.9333333335 + x = -1.292714629 Solving -0.9333333335 + x = -1.292714629 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.9333333335' to each side of the equation. -0.9333333335 + 0.9333333335 + x = -1.292714629 + 0.9333333335 Combine like terms: -0.9333333335 + 0.9333333335 = 0.0000000000 0.0000000000 + x = -1.292714629 + 0.9333333335 x = -1.292714629 + 0.9333333335 Combine like terms: -1.292714629 + 0.9333333335 = -0.3593812955 x = -0.3593812955 Simplifying x = -0.3593812955

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.2260479625, -0.3593812955}

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