-10h(h-99)=80

Solution for -10h(h-99)=80 equation:

-10h(h-99)=80

We move all terms to the left:

-10h(h-99)-(80)=0

We multiply parentheses

-10h^2+990h-80=0

a = -10; b = 990; c = -80;
Δ = b2-4ac
Δ = 9902-4·(-10)·(-80)
Δ = 976900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$h_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$h_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{976900}=\sqrt{100*9769}=\sqrt{100}*\sqrt{9769}=10\sqrt{9769}$
$h_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(990)-10\sqrt{9769}}{2*-10}=\frac{-990-10\sqrt{9769}}{-20}
$
$h_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(990)+10\sqrt{9769}}{2*-10}=\frac{-990+10\sqrt{9769}}{-20}
$