-324=20t-5t^2

Solution for -324=20t-5t^2 equation:

-324=20t-5t^2

We move all terms to the left:

-324-(20t-5t^2)=0

We get rid of parentheses

5t^2-20t-324=0

a = 5; b = -20; c = -324;
Δ = b2-4ac
Δ = -202-4·5·(-324)
Δ = 6880
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:

$\sqrt{\Delta}=\sqrt{6880}=\sqrt{16*430}=\sqrt{16}*\sqrt{430}=4\sqrt{430}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-4\sqrt{430}}{2*5}=\frac{20-4\sqrt{430}}{10}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+4\sqrt{430}}{2*5}=\frac{20+4\sqrt{430}}{10}
$