6t^2+12t-15=0

Solution for 6t^2+12t-15=0 equation:

Simplifying
6t2 + 12t + -15 = 0

Reorder the terms:
-15 + 12t + 6t2 = 0

Solving
-15 + 12t + 6t2 = 0

Solving for variable 't'.

Factor out the Greatest Common Factor (GCF), '3'.
3(-5 + 4t + 2t2) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(-5 + 4t + 2t2)' equal to zero and attempt to solve:

Simplifying
-5 + 4t + 2t2 = 0

Solving
-5 + 4t + 2t2 = 0

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

Divide each side by '2'.
-2.5 + 2t + t2 = 0

Move the constant term to the right:

Add '2.5' to each side of the equation.
-2.5 + 2t + 2.5 + t2 = 0 + 2.5

Reorder the terms:
-2.5 + 2.5 + 2t + t2 = 0 + 2.5

Combine like terms: -2.5 + 2.5 = 0.0
0.0 + 2t + t2 = 0 + 2.5
2t + t2 = 0 + 2.5

Combine like terms: 0 + 2.5 = 2.5
2t + t2 = 2.5

The t term is 2t.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2t + 1 + t2 = 2.5 + 1

Reorder the terms:
1 + 2t + t2 = 2.5 + 1

Combine like terms: 2.5 + 1 = 3.5
1 + 2t + t2 = 3.5

Factor a perfect square on the left side:
(t + 1)(t + 1) = 3.5

Calculate the square root of the right side: 1.870828693

Break this problem into two subproblems by setting 
(t + 1) equal to 1.870828693 and -1.870828693.

Subproblem 1
t + 1 = 1.870828693

Simplifying
t + 1 = 1.870828693

Reorder the terms:
1 + t = 1.870828693

Solving
1 + t = 1.870828693

Solving for variable 't'.

Move all terms containing t to the left, all other terms to the right.

Add '-1' to each side of the equation.
1 + -1 + t = 1.870828693 + -1

Combine like terms: 1 + -1 = 0
0 + t = 1.870828693 + -1
t = 1.870828693 + -1

Combine like terms: 1.870828693 + -1 = 0.870828693
t = 0.870828693

Simplifying
t = 0.870828693

Subproblem 2
t + 1 = -1.870828693

Simplifying
t + 1 = -1.870828693

Reorder the terms:
1 + t = -1.870828693

Solving
1 + t = -1.870828693

Solving for variable 't'.

Move all terms containing t to the left, all other terms to the right.

Add '-1' to each side of the equation.
1 + -1 + t = -1.870828693 + -1

Combine like terms: 1 + -1 = 0
0 + t = -1.870828693 + -1
t = -1.870828693 + -1

Combine like terms: -1.870828693 + -1 = -2.870828693
t = -2.870828693

Simplifying
t = -2.870828693

Solution
The solution to the problem is based on the solutions
from the subproblems.
t = {0.870828693, -2.870828693}
Solution
t = {0.870828693, -2.870828693}