940=1800-16t^2

Solution for 940=1800-16t^2 equation:

940=1800-16t^2

We move all terms to the left:

940-(1800-16t^2)=0

We get rid of parentheses

16t^2-1800+940=0

We add all the numbers together, and all the variables

16t^2-860=0

a = 16; b = 0; c = -860;
Δ = b2-4ac
Δ = 02-4·16·(-860)
Δ = 55040
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:

$\sqrt{\Delta}=\sqrt{55040}=\sqrt{256*215}=\sqrt{256}*\sqrt{215}=16\sqrt{215}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-16\sqrt{215}}{2*16}=\frac{0-16\sqrt{215}}{32}
=-\frac{16\sqrt{215}}{32}
=-\frac{\sqrt{215}}{2}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+16\sqrt{215}}{2*16}=\frac{0+16\sqrt{215}}{32}
=\frac{16\sqrt{215}}{32}
=\frac{\sqrt{215}}{2}
$