H=25t-4.9t^2

Solution for H=25t-4.9t^2 equation:

=25H-4.9H^2

We move all terms to the left:

-(25H-4.9H^2)=0

We get rid of parentheses

4.9H^2-25H=0

a = 4.9; b = -25; c = 0;
Δ = b2-4ac
Δ = -252-4·4.9·0
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-25)-25}{2*4.9}=\frac{0}{9.8}
=0
$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-25)+25}{2*4.9}=\frac{50}{9.8}
=5+1/9.8
$