H=-4.9t^2-4t+4

Solution for H=-4.9t^2-4t+4 equation:

=-4.9H^2-4H+4

We move all terms to the left:

-(-4.9H^2-4H+4)=0

We get rid of parentheses

4.9H^2+4H-4=0

a = 4.9; b = 4; c = -4;
Δ = b2-4ac
Δ = 42-4·4.9·(-4)
Δ = 94.4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-\sqrt{94.4}}{2*4.9}=\frac{-4-\sqrt{94.4}}{9.8}
$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+\sqrt{94.4}}{2*4.9}=\frac{-4+\sqrt{94.4}}{9.8}
$