8=3+15t-5t^2

Solution for 8=3+15t-5t^2 equation:

Simplifying
8 = 3 + 15t + -5t2

Solving
8 = 3 + 15t + -5t2

Solving for variable 't'.

Combine like terms: 8 + -3 = 5
5 + -15t + 5t2 = 3 + 15t + -5t2 + -3 + -15t + 5t2

Reorder the terms:
5 + -15t + 5t2 = 3 + -3 + 15t + -15t + -5t2 + 5t2

Combine like terms: 3 + -3 = 0
5 + -15t + 5t2 = 0 + 15t + -15t + -5t2 + 5t2
5 + -15t + 5t2 = 15t + -15t + -5t2 + 5t2

Combine like terms: 15t + -15t = 0
5 + -15t + 5t2 = 0 + -5t2 + 5t2
5 + -15t + 5t2 = -5t2 + 5t2

Combine like terms: -5t2 + 5t2 = 0
5 + -15t + 5t2 = 0

Factor out the Greatest Common Factor (GCF), '5'.
5(1 + -3t + t2) = 0

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

Simplifying
1 + -3t + t2 = 0

Solving
1 + -3t + t2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-1' to each side of the equation.
1 + -3t + -1 + t2 = 0 + -1

Reorder the terms:
1 + -1 + -3t + t2 = 0 + -1

Combine like terms: 1 + -1 = 0
0 + -3t + t2 = 0 + -1
-3t + t2 = 0 + -1

Combine like terms: 0 + -1 = -1
-3t + t2 = -1

The t term is -3t.  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.
-3t + 2.25 + t2 = -1 + 2.25

Reorder the terms:
2.25 + -3t + t2 = -1 + 2.25

Combine like terms: -1 + 2.25 = 1.25
2.25 + -3t + t2 = 1.25

Factor a perfect square on the left side:
(t + -1.5)(t + -1.5) = 1.25

Calculate the square root of the right side: 1.118033989

Break this problem into two subproblems by setting 
(t + -1.5) equal to 1.118033989 and -1.118033989.

Subproblem 1
t + -1.5 = 1.118033989

Simplifying
t + -1.5 = 1.118033989

Reorder the terms:
-1.5 + t = 1.118033989

Solving
-1.5 + t = 1.118033989

Solving for variable 't'.

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

Add '1.5' to each side of the equation.
-1.5 + 1.5 + t = 1.118033989 + 1.5

Combine like terms: -1.5 + 1.5 = 0.0
0.0 + t = 1.118033989 + 1.5
t = 1.118033989 + 1.5

Combine like terms: 1.118033989 + 1.5 = 2.618033989
t = 2.618033989

Simplifying
t = 2.618033989

Subproblem 2
t + -1.5 = -1.118033989

Simplifying
t + -1.5 = -1.118033989

Reorder the terms:
-1.5 + t = -1.118033989

Solving
-1.5 + t = -1.118033989

Solving for variable 't'.

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

Add '1.5' to each side of the equation.
-1.5 + 1.5 + t = -1.118033989 + 1.5

Combine like terms: -1.5 + 1.5 = 0.0
0.0 + t = -1.118033989 + 1.5
t = -1.118033989 + 1.5

Combine like terms: -1.118033989 + 1.5 = 0.381966011
t = 0.381966011

Simplifying
t = 0.381966011

Solution
The solution to the problem is based on the solutions
from the subproblems.
t = {2.618033989, 0.381966011}
Solution
t = {2.618033989, 0.381966011}