-15c(c-8)=0

Solution for -15c(c-8)=0 equation:

-15c(c-8)=0

We multiply parentheses

-15c^2+120c=0

a = -15; b = 120; c = 0;
Δ = b2-4ac
Δ = 1202-4·(-15)·0
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(120)-120}{2*-15}=\frac{-240}{-30}
=+8
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+120}{2*-15}=\frac{0}{-30}
=0
$