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

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

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

-5(-1v^2-1v-4v-4)=0

We multiply parentheses

5v^2+5v+20v+20=0

We add all the numbers together, and all the variables

5v^2+25v+20=0

a = 5; b = 25; c = +20;
Δ = b2-4ac
Δ = 252-4·5·20
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-15}{2*5}=\frac{-40}{10}
=-4
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+15}{2*5}=\frac{-10}{10}
=-1
$