0=30.6t-4.9t^2

Solution for 0=30.6t-4.9t^2 equation:

0=30.6t-4.9t^2

We move all terms to the left:

0-(30.6t-4.9t^2)=0

We add all the numbers together, and all the variables

-(30.6t-4.9t^2)=0

We get rid of parentheses

4.9t^2-30.6t=0

a = 4.9; b = -30.6; c = 0;
Δ = b2-4ac
Δ = -30.62-4·4.9·0
Δ = 936.36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30.6)-\sqrt{936.36}}{2*4.9}=\frac{30.6-\sqrt{936.36}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30.6)+\sqrt{936.36}}{2*4.9}=\frac{30.6+\sqrt{936.36}}{9.8}
$