y*(y+15)=0

Solution for y*(y+15)=0 equation:

y(y+15)=0

We multiply parentheses

y^2+15y=0

a = 1; b = 15; c = 0;
Δ = b2-4ac
Δ = 152-4·1·0
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*1}=\frac{-30}{2}
=-15
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+15}{2*1}=\frac{0}{2}
=0
$