0=4.9t^2-20t

Solution for 0=4.9t^2-20t equation:

0=4.9t^2-20t

We move all terms to the left:

0-(4.9t^2-20t)=0

We add all the numbers together, and all the variables

-(4.9t^2-20t)=0

We get rid of parentheses

-4.9t^2+20t=0

a = -4.9; b = 20; c = 0;
Δ = b2-4ac
Δ = 202-4·(-4.9)·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-20}{2*-4.9}=\frac{-40}{-9.8}
=4+0.8/9.8
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+20}{2*-4.9}=\frac{0}{-9.8}
=0
$