Y=5+80x-16x^2

Solution for Y=5+80x-16x^2 equation:

=5+80Y-16Y^2

We move all terms to the left:

-(5+80Y-16Y^2)=0

We get rid of parentheses

16Y^2-80Y-5=0

a = 16; b = -80; c = -5;
Δ = b2-4ac
Δ = -802-4·16·(-5)
Δ = 6720
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{6720}=\sqrt{64*105}=\sqrt{64}*\sqrt{105}=8\sqrt{105}$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-80)-8\sqrt{105}}{2*16}=\frac{80-8\sqrt{105}}{32}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-80)+8\sqrt{105}}{2*16}=\frac{80+8\sqrt{105}}{32}
$