500=4.9t^2

Solution for 500=4.9t^2 equation:

500=4.9t^2

We move all terms to the left:

500-(4.9t^2)=0

We get rid of parentheses

-4.9t^2+500=0

a = -4.9; b = 0; c = +500;
Δ = b2-4ac
Δ = 02-4·(-4.9)·500
Δ = 9800
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:

$\sqrt{\Delta}=\sqrt{9800}=\sqrt{4900*2}=\sqrt{4900}*\sqrt{2}=70\sqrt{2}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-70\sqrt{2}}{2*-4.9}=\frac{0-70\sqrt{2}}{-9.8}
=-\frac{70\sqrt{2}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+70\sqrt{2}}{2*-4.9}=\frac{0+70\sqrt{2}}{-9.8}
=\frac{70\sqrt{2}}{-9.8}
$