3x^2-39x-7=0

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Solution for 3x^2-39x-7=0 equation:


Simplifying
3x2 + -39x + -7 = 0

Reorder the terms:
-7 + -39x + 3x2 = 0

Solving
-7 + -39x + 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'.
-2.333333333 + -13x + x2 = 0

Move the constant term to the right:

Add '2.333333333' to each side of the equation.
-2.333333333 + -13x + 2.333333333 + x2 = 0 + 2.333333333

Reorder the terms:
-2.333333333 + 2.333333333 + -13x + x2 = 0 + 2.333333333

Combine like terms: -2.333333333 + 2.333333333 = 0.000000000
0.000000000 + -13x + x2 = 0 + 2.333333333
-13x + x2 = 0 + 2.333333333

Combine like terms: 0 + 2.333333333 = 2.333333333
-13x + x2 = 2.333333333

The x term is -13x.  Take half its coefficient (-6.5).
Square it (42.25) and add it to both sides.

Add '42.25' to each side of the equation.
-13x + 42.25 + x2 = 2.333333333 + 42.25

Reorder the terms:
42.25 + -13x + x2 = 2.333333333 + 42.25

Combine like terms: 2.333333333 + 42.25 = 44.583333333
42.25 + -13x + x2 = 44.583333333

Factor a perfect square on the left side:
(x + -6.5)(x + -6.5) = 44.583333333

Calculate the square root of the right side: 6.677075208

Break this problem into two subproblems by setting 
(x + -6.5) equal to 6.677075208 and -6.677075208.

Subproblem 1

x + -6.5 = 6.677075208 Simplifying x + -6.5 = 6.677075208 Reorder the terms: -6.5 + x = 6.677075208 Solving -6.5 + x = 6.677075208 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '6.5' to each side of the equation. -6.5 + 6.5 + x = 6.677075208 + 6.5 Combine like terms: -6.5 + 6.5 = 0.0 0.0 + x = 6.677075208 + 6.5 x = 6.677075208 + 6.5 Combine like terms: 6.677075208 + 6.5 = 13.177075208 x = 13.177075208 Simplifying x = 13.177075208

Subproblem 2

x + -6.5 = -6.677075208 Simplifying x + -6.5 = -6.677075208 Reorder the terms: -6.5 + x = -6.677075208 Solving -6.5 + x = -6.677075208 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '6.5' to each side of the equation. -6.5 + 6.5 + x = -6.677075208 + 6.5 Combine like terms: -6.5 + 6.5 = 0.0 0.0 + x = -6.677075208 + 6.5 x = -6.677075208 + 6.5 Combine like terms: -6.677075208 + 6.5 = -0.177075208 x = -0.177075208 Simplifying x = -0.177075208

Solution

The solution to the problem is based on the solutions from the subproblems. x = {13.177075208, -0.177075208}

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