3x^2-15x-4=0

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Solution for 3x^2-15x-4=0 equation:


Simplifying
3x2 + -15x + -4 = 0

Reorder the terms:
-4 + -15x + 3x2 = 0

Solving
-4 + -15x + 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'.
-1.333333333 + -5x + x2 = 0

Move the constant term to the right:

Add '1.333333333' to each side of the equation.
-1.333333333 + -5x + 1.333333333 + x2 = 0 + 1.333333333

Reorder the terms:
-1.333333333 + 1.333333333 + -5x + x2 = 0 + 1.333333333

Combine like terms: -1.333333333 + 1.333333333 = 0.000000000
0.000000000 + -5x + x2 = 0 + 1.333333333
-5x + x2 = 0 + 1.333333333

Combine like terms: 0 + 1.333333333 = 1.333333333
-5x + x2 = 1.333333333

The x term is -5x.  Take half its coefficient (-2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
-5x + 6.25 + x2 = 1.333333333 + 6.25

Reorder the terms:
6.25 + -5x + x2 = 1.333333333 + 6.25

Combine like terms: 1.333333333 + 6.25 = 7.583333333
6.25 + -5x + x2 = 7.583333333

Factor a perfect square on the left side:
(x + -2.5)(x + -2.5) = 7.583333333

Calculate the square root of the right side: 2.753785274

Break this problem into two subproblems by setting 
(x + -2.5) equal to 2.753785274 and -2.753785274.

Subproblem 1

x + -2.5 = 2.753785274 Simplifying x + -2.5 = 2.753785274 Reorder the terms: -2.5 + x = 2.753785274 Solving -2.5 + x = 2.753785274 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.5' to each side of the equation. -2.5 + 2.5 + x = 2.753785274 + 2.5 Combine like terms: -2.5 + 2.5 = 0.0 0.0 + x = 2.753785274 + 2.5 x = 2.753785274 + 2.5 Combine like terms: 2.753785274 + 2.5 = 5.253785274 x = 5.253785274 Simplifying x = 5.253785274

Subproblem 2

x + -2.5 = -2.753785274 Simplifying x + -2.5 = -2.753785274 Reorder the terms: -2.5 + x = -2.753785274 Solving -2.5 + x = -2.753785274 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.5' to each side of the equation. -2.5 + 2.5 + x = -2.753785274 + 2.5 Combine like terms: -2.5 + 2.5 = 0.0 0.0 + x = -2.753785274 + 2.5 x = -2.753785274 + 2.5 Combine like terms: -2.753785274 + 2.5 = -0.253785274 x = -0.253785274 Simplifying x = -0.253785274

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.253785274, -0.253785274}

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