H=-2.5t^2+200t

Solution for H=-2.5t^2+200t equation:

=-2.5H^2+200H

We move all terms to the left:

-(-2.5H^2+200H)=0

We get rid of parentheses

2.5H^2-200H=0

a = 2.5; b = -200; c = 0;
Δ = b2-4ac
Δ = -2002-4·2.5·0
Δ = 40000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{40000}=200$
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-200)-200}{2*2.5}=\frac{0}{5}
=0
$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-200)+200}{2*2.5}=\frac{400}{5}
=80
$