0=640-16t^2

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

0=640-16t^2

We move all terms to the left:

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

We add all the numbers together, and all the variables

-(640-16t^2)=0

We get rid of parentheses

16t^2-640=0

a = 16; b = 0; c = -640;
Δ = b2-4ac
Δ = 02-4·16·(-640)
Δ = 40960
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:

$\sqrt{\Delta}=\sqrt{40960}=\sqrt{4096*10}=\sqrt{4096}*\sqrt{10}=64\sqrt{10}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-64\sqrt{10}}{2*16}=\frac{0-64\sqrt{10}}{32}
=-\frac{64\sqrt{10}}{32}
=-2\sqrt{10}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+64\sqrt{10}}{2*16}=\frac{0+64\sqrt{10}}{32}
=\frac{64\sqrt{10}}{32}
=2\sqrt{10}
$