-3y(2y+5)=0

Solution for -3y(2y+5)=0 equation:

-3y(2y+5)=0

We multiply parentheses

-6y^2-15y=0

a = -6; b = -15; c = 0;
Δ = b2-4ac
Δ = -152-4·(-6)·0
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-15}{2*-6}=\frac{0}{-12}
=0
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+15}{2*-6}=\frac{30}{-12}
=-2+1/2
$