80=-16x^2+128x

Solution for 80=-16x^2+128x equation:

80=-16x^2+128x

We move all terms to the left:

80-(-16x^2+128x)=0

We get rid of parentheses

16x^2-128x+80=0

a = 16; b = -128; c = +80;
Δ = b2-4ac
Δ = -1282-4·16·80
Δ = 11264
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{11264}=\sqrt{1024*11}=\sqrt{1024}*\sqrt{11}=32\sqrt{11}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-128)-32\sqrt{11}}{2*16}=\frac{128-32\sqrt{11}}{32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-128)+32\sqrt{11}}{2*16}=\frac{128+32\sqrt{11}}{32}
$