0=100x-20x^2-80

Solution for 0=100x-20x^2-80 equation:

0=100x-20x^2-80

We move all terms to the left:

0-(100x-20x^2-80)=0

We add all the numbers together, and all the variables

-(100x-20x^2-80)=0

We get rid of parentheses

20x^2-100x+80=0

a = 20; b = -100; c = +80;
Δ = b2-4ac
Δ = -1002-4·20·80
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-100)-60}{2*20}=\frac{40}{40}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-100)+60}{2*20}=\frac{160}{40}
=4
$