5x^2+15x+8=0

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Solution for 5x^2+15x+8=0 equation:


Simplifying
5x2 + 15x + 8 = 0

Reorder the terms:
8 + 15x + 5x2 = 0

Solving
8 + 15x + 5x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
5 the coefficient of the squared term: 

Divide each side by '5'.
1.6 + 3x + x2 = 0

Move the constant term to the right:

Add '-1.6' to each side of the equation.
1.6 + 3x + -1.6 + x2 = 0 + -1.6

Reorder the terms:
1.6 + -1.6 + 3x + x2 = 0 + -1.6

Combine like terms: 1.6 + -1.6 = 0.0
0.0 + 3x + x2 = 0 + -1.6
3x + x2 = 0 + -1.6

Combine like terms: 0 + -1.6 = -1.6
3x + x2 = -1.6

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = -1.6 + 2.25

Reorder the terms:
2.25 + 3x + x2 = -1.6 + 2.25

Combine like terms: -1.6 + 2.25 = 0.65
2.25 + 3x + x2 = 0.65

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 0.65

Calculate the square root of the right side: 0.806225775

Break this problem into two subproblems by setting 
(x + 1.5) equal to 0.806225775 and -0.806225775.

Subproblem 1

x + 1.5 = 0.806225775 Simplifying x + 1.5 = 0.806225775 Reorder the terms: 1.5 + x = 0.806225775 Solving 1.5 + x = 0.806225775 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = 0.806225775 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 0.806225775 + -1.5 x = 0.806225775 + -1.5 Combine like terms: 0.806225775 + -1.5 = -0.693774225 x = -0.693774225 Simplifying x = -0.693774225

Subproblem 2

x + 1.5 = -0.806225775 Simplifying x + 1.5 = -0.806225775 Reorder the terms: 1.5 + x = -0.806225775 Solving 1.5 + x = -0.806225775 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = -0.806225775 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -0.806225775 + -1.5 x = -0.806225775 + -1.5 Combine like terms: -0.806225775 + -1.5 = -2.306225775 x = -2.306225775 Simplifying x = -2.306225775

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.693774225, -2.306225775}

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