15x^2+15x+18=0

Solution for 15x^2+15x+18=0 equation:

Simplifying
15x2 + 15x + 18 = 0

Reorder the terms:
18 + 15x + 15x2 = 0

Solving
18 + 15x + 15x2 = 0

Solving for variable 'x'.

Factor out the Greatest Common Factor (GCF), '3'.
3(6 + 5x + 5x2) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(6 + 5x + 5x2)' equal to zero and attempt to solve:

Simplifying
6 + 5x + 5x2 = 0

Solving
6 + 5x + 5x2 = 0

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

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

Move the constant term to the right:

Add '-1.2' to each side of the equation.
1.2 + x + -1.2 + x2 = 0 + -1.2

Reorder the terms:
1.2 + -1.2 + x + x2 = 0 + -1.2

Combine like terms: 1.2 + -1.2 = 0.0
0.0 + x + x2 = 0 + -1.2
x + x2 = 0 + -1.2

Combine like terms: 0 + -1.2 = -1.2
x + x2 = -1.2

The x term is x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
 + 0.25 + x2 = -1.2 + 0.25

Combine like terms:  + 0.25 = 1.25
1.25 + x2 = -1.2 + 0.25

Combine like terms: -1.2 + 0.25 = -0.95
1.25 + x2 = -0.95

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = -0.95

Can't calculate square root of the right side.

The solution to this equation could not be determined.

This subproblem is being ignored because a solution could not be determined.

The solution to this equation could not be determined.