-30n(n+2)=0

Solution for -30n(n+2)=0 equation:

-30n(n+2)=0

We multiply parentheses

-30n^2-60n=0

a = -30; b = -60; c = 0;
Δ = b2-4ac
Δ = -602-4·(-30)·0
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-60}{2*-30}=\frac{0}{-60}
=0
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+60}{2*-30}=\frac{120}{-60}
=-2
$