-4x^2+600-20x=0

Solution for -4x^2+600-20x=0 equation:

-4x^2+600-20x=0

a = -4; b = -20; c = +600;
Δ = b2-4ac
Δ = -202-4·(-4)·600
Δ = 10000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{10000}=100$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-100}{2*-4}=\frac{-80}{-8}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+100}{2*-4}=\frac{120}{-8}
=-15
$