3x^2+39x-40=0

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Solution for 3x^2+39x-40=0 equation:


Simplifying
3x2 + 39x + -40 = 0

Reorder the terms:
-40 + 39x + 3x2 = 0

Solving
-40 + 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'.
-13.33333333 + 13x + x2 = 0

Move the constant term to the right:

Add '13.33333333' to each side of the equation.
-13.33333333 + 13x + 13.33333333 + x2 = 0 + 13.33333333

Reorder the terms:
-13.33333333 + 13.33333333 + 13x + x2 = 0 + 13.33333333

Combine like terms: -13.33333333 + 13.33333333 = 0.00000000
0.00000000 + 13x + x2 = 0 + 13.33333333
13x + x2 = 0 + 13.33333333

Combine like terms: 0 + 13.33333333 = 13.33333333
13x + x2 = 13.33333333

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 = 13.33333333 + 42.25

Reorder the terms:
42.25 + 13x + x2 = 13.33333333 + 42.25

Combine like terms: 13.33333333 + 42.25 = 55.58333333
42.25 + 13x + x2 = 55.58333333

Factor a perfect square on the left side:
(x + 6.5)(x + 6.5) = 55.58333333

Calculate the square root of the right side: 7.455423082

Break this problem into two subproblems by setting 
(x + 6.5) equal to 7.455423082 and -7.455423082.

Subproblem 1

x + 6.5 = 7.455423082 Simplifying x + 6.5 = 7.455423082 Reorder the terms: 6.5 + x = 7.455423082 Solving 6.5 + x = 7.455423082 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 = 7.455423082 + -6.5 Combine like terms: 6.5 + -6.5 = 0.0 0.0 + x = 7.455423082 + -6.5 x = 7.455423082 + -6.5 Combine like terms: 7.455423082 + -6.5 = 0.955423082 x = 0.955423082 Simplifying x = 0.955423082

Subproblem 2

x + 6.5 = -7.455423082 Simplifying x + 6.5 = -7.455423082 Reorder the terms: 6.5 + x = -7.455423082 Solving 6.5 + x = -7.455423082 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 = -7.455423082 + -6.5 Combine like terms: 6.5 + -6.5 = 0.0 0.0 + x = -7.455423082 + -6.5 x = -7.455423082 + -6.5 Combine like terms: -7.455423082 + -6.5 = -13.955423082 x = -13.955423082 Simplifying x = -13.955423082

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.955423082, -13.955423082}

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