2000=-0.004x^2+8x-80

Solution for 2000=-0.004x^2+8x-80 equation:

2000=-0.004x^2+8x-80

We move all terms to the left:

2000-(-0.004x^2+8x-80)=0

We get rid of parentheses

0.004x^2-8x+80+2000=0

We add all the numbers together, and all the variables

0.004x^2-8x+2080=0

a = 0.004; b = -8; c = +2080;
Δ = b2-4ac
Δ = -82-4·0.004·2080
Δ = 30.72
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-\sqrt{30.72}}{2*0.004}=\frac{8-\sqrt{30.72}}{0.008}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+\sqrt{30.72}}{2*0.004}=\frac{8+\sqrt{30.72}}{0.008}
$