3x^2+20x+15=0

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Solution for 3x^2+20x+15=0 equation:


Simplifying
3x2 + 20x + 15 = 0

Reorder the terms:
15 + 20x + 3x2 = 0

Solving
15 + 20x + 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'.
5 + 6.666666667x + x2 = 0

Move the constant term to the right:

Add '-5' to each side of the equation.
5 + 6.666666667x + -5 + x2 = 0 + -5

Reorder the terms:
5 + -5 + 6.666666667x + x2 = 0 + -5

Combine like terms: 5 + -5 = 0
0 + 6.666666667x + x2 = 0 + -5
6.666666667x + x2 = 0 + -5

Combine like terms: 0 + -5 = -5
6.666666667x + x2 = -5

The x term is 6.666666667x.  Take half its coefficient (3.333333334).
Square it (11.11111112) and add it to both sides.

Add '11.11111112' to each side of the equation.
6.666666667x + 11.11111112 + x2 = -5 + 11.11111112

Reorder the terms:
11.11111112 + 6.666666667x + x2 = -5 + 11.11111112

Combine like terms: -5 + 11.11111112 = 6.11111112
11.11111112 + 6.666666667x + x2 = 6.11111112

Factor a perfect square on the left side:
(x + 3.333333334)(x + 3.333333334) = 6.11111112

Calculate the square root of the right side: 2.472066164

Break this problem into two subproblems by setting 
(x + 3.333333334) equal to 2.472066164 and -2.472066164.

Subproblem 1

x + 3.333333334 = 2.472066164 Simplifying x + 3.333333334 = 2.472066164 Reorder the terms: 3.333333334 + x = 2.472066164 Solving 3.333333334 + x = 2.472066164 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.333333334' to each side of the equation. 3.333333334 + -3.333333334 + x = 2.472066164 + -3.333333334 Combine like terms: 3.333333334 + -3.333333334 = 0.000000000 0.000000000 + x = 2.472066164 + -3.333333334 x = 2.472066164 + -3.333333334 Combine like terms: 2.472066164 + -3.333333334 = -0.86126717 x = -0.86126717 Simplifying x = -0.86126717

Subproblem 2

x + 3.333333334 = -2.472066164 Simplifying x + 3.333333334 = -2.472066164 Reorder the terms: 3.333333334 + x = -2.472066164 Solving 3.333333334 + x = -2.472066164 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.333333334' to each side of the equation. 3.333333334 + -3.333333334 + x = -2.472066164 + -3.333333334 Combine like terms: 3.333333334 + -3.333333334 = 0.000000000 0.000000000 + x = -2.472066164 + -3.333333334 x = -2.472066164 + -3.333333334 Combine like terms: -2.472066164 + -3.333333334 = -5.805399498 x = -5.805399498 Simplifying x = -5.805399498

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.86126717, -5.805399498}

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