120=2h^2+10h

Solution for 120=2h^2+10h equation:

120=2h^2+10h

We move all terms to the left:

120-(2h^2+10h)=0

We get rid of parentheses

-2h^2-10h+120=0

a = -2; b = -10; c = +120;
Δ = b2-4ac
Δ = -102-4·(-2)·120
Δ = 1060
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:

$\sqrt{\Delta}=\sqrt{1060}=\sqrt{4*265}=\sqrt{4}*\sqrt{265}=2\sqrt{265}$
$h_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-2\sqrt{265}}{2*-2}=\frac{10-2\sqrt{265}}{-4}
$
$h_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+2\sqrt{265}}{2*-2}=\frac{10+2\sqrt{265}}{-4}
$