0=-16t^2+64t+85

Solution for 0=-16t^2+64t+85 equation:

0=-16t^2+64t+85

We move all terms to the left:

0-(-16t^2+64t+85)=0

We add all the numbers together, and all the variables

-(-16t^2+64t+85)=0

We get rid of parentheses

16t^2-64t-85=0

a = 16; b = -64; c = -85;
Δ = b2-4ac
Δ = -642-4·16·(-85)
Δ = 9536
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{9536}=\sqrt{64*149}=\sqrt{64}*\sqrt{149}=8\sqrt{149}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-64)-8\sqrt{149}}{2*16}=\frac{64-8\sqrt{149}}{32}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-64)+8\sqrt{149}}{2*16}=\frac{64+8\sqrt{149}}{32}
$