0=-3x2+240x-800

Solution for 0=-3x2+240x-800 equation:

0=-3x^2+240x-800

We move all terms to the left:

0-(-3x^2+240x-800)=0

We add all the numbers together, and all the variables

-(-3x^2+240x-800)=0

We get rid of parentheses

3x^2-240x+800=0

a = 3; b = -240; c = +800;
Δ = b2-4ac
Δ = -2402-4·3·800
Δ = 48000
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:

$\sqrt{\Delta}=\sqrt{48000}=\sqrt{1600*30}=\sqrt{1600}*\sqrt{30}=40\sqrt{30}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-240)-40\sqrt{30}}{2*3}=\frac{240-40\sqrt{30}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-240)+40\sqrt{30}}{2*3}=\frac{240+40\sqrt{30}}{6}
$