-20x=5x^2

Solution for -20x=5x^2 equation:

-20x=5x^2

We move all terms to the left:

-20x-(5x^2)=0

determiningTheFunctionDomain
-5x^2-20x=0

a = -5; b = -20; c = 0;
Δ = b2-4ac
Δ = -202-4·(-5)·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-20}{2*-5}=\frac{0}{-10}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+20}{2*-5}=\frac{40}{-10}
=-4
$