c(15c-30)=0

Solution for c(15c-30)=0 equation:

c(15c-30)=0

We multiply parentheses

15c^2-30c=0

a = 15; b = -30; c = 0;
Δ = b2-4ac
Δ = -302-4·15·0
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-30}{2*15}=\frac{0}{30}
=0
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+30}{2*15}=\frac{60}{30}
=2
$