0=-16t^2+64t+640

Solution for 0=-16t^2+64t+640 equation:

0=-16t^2+64t+640

We move all terms to the left:

0-(-16t^2+64t+640)=0

We add all the numbers together, and all the variables

-(-16t^2+64t+640)=0

We get rid of parentheses

16t^2-64t-640=0

a = 16; b = -64; c = -640;
Δ = b2-4ac
Δ = -642-4·16·(-640)
Δ = 45056
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:

$\sqrt{\Delta}=\sqrt{45056}=\sqrt{4096*11}=\sqrt{4096}*\sqrt{11}=64\sqrt{11}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-64)-64\sqrt{11}}{2*16}=\frac{64-64\sqrt{11}}{32}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-64)+64\sqrt{11}}{2*16}=\frac{64+64\sqrt{11}}{32}
$