0=6.8t+8.5t^2

Solution for 0=6.8t+8.5t^2 equation:

0=6.8t+8.5t^2

We move all terms to the left:

0-(6.8t+8.5t^2)=0

We add all the numbers together, and all the variables

-(6.8t+8.5t^2)=0

We get rid of parentheses

-8.5t^2-6.8t=0

a = -8.5; b = -6.8; c = 0;
Δ = b2-4ac
Δ = -6.82-4·(-8.5)·0
Δ = 46.24
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6.8)-\sqrt{46.24}}{2*-8.5}=\frac{6.8-\sqrt{46.24}}{-17}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6.8)+\sqrt{46.24}}{2*-8.5}=\frac{6.8+\sqrt{46.24}}{-17}
$