-0,4x^2+240x-2000=0

Solution for -0,4x^2+240x-2000=0 equation:

-0.4x^2+240x-2000=0

a = -0.4; b = 240; c = -2000;
Δ = b2-4ac
Δ = 2402-4·(-0.4)·(-2000)
Δ = 54400
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:

$\sqrt{\Delta}=\sqrt{54400}=\sqrt{1600*34}=\sqrt{1600}*\sqrt{34}=40\sqrt{34}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(240)-40\sqrt{34}}{2*-0.4}=\frac{-240-40\sqrt{34}}{-0.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(240)+40\sqrt{34}}{2*-0.4}=\frac{-240+40\sqrt{34}}{-0.8}
$