3(y+8)(-y-5)=0

Solution for 3(y+8)(-y-5)=0 equation:

3(y+8)(-y-5)=0

We add all the numbers together, and all the variables

3(y+8)(-1y-5)=0

We multiply parentheses ..

3(-1y^2-5y-8y-40)=0

We multiply parentheses

-3y^2-15y-24y-120=0

We add all the numbers together, and all the variables

-3y^2-39y-120=0

a = -3; b = -39; c = -120;
Δ = b2-4ac
Δ = -392-4·(-3)·(-120)
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39)-9}{2*-3}=\frac{30}{-6}
=-5
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39)+9}{2*-3}=\frac{48}{-6}
=-8
$