0=300-20x-4.905x^2

Solution for 0=300-20x-4.905x^2 equation:

0=300-20x-4.905x^2

We move all terms to the left:

0-(300-20x-4.905x^2)=0

We add all the numbers together, and all the variables

-(300-20x-4.905x^2)=0

We get rid of parentheses

4.905x^2+20x-300=0

a = 4.905; b = 20; c = -300;
Δ = b2-4ac
Δ = 202-4·4.905·(-300)
Δ = 6286
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-\sqrt{6286}}{2*4.905}=\frac{-20-\sqrt{6286}}{9.81}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+\sqrt{6286}}{2*4.905}=\frac{-20+\sqrt{6286}}{9.81}
$