-5(y+4)(-y+1)=0

Solution for -5(y+4)(-y+1)=0 equation:

-5(y+4)(-y+1)=0

We add all the numbers together, and all the variables

-5(y+4)(-1y+1)=0

We multiply parentheses ..

-5(-1y^2+y-4y+4)=0

We multiply parentheses

5y^2-5y+20y-20=0

We add all the numbers together, and all the variables

5y^2+15y-20=0

a = 5; b = 15; c = -20;
Δ = b2-4ac
Δ = 152-4·5·(-20)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-25}{2*5}=\frac{-40}{10}
=-4
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+25}{2*5}=\frac{10}{10}
=1
$