-2(v+3)(-v-7)=0

Solution for -2(v+3)(-v-7)=0 equation:

-2(v+3)(-v-7)=0

We add all the numbers together, and all the variables

-2(v+3)(-1v-7)=0

We multiply parentheses ..

-2(-1v^2-7v-3v-21)=0

We multiply parentheses

2v^2+14v+6v+42=0

We add all the numbers together, and all the variables

2v^2+20v+42=0

a = 2; b = 20; c = +42;
Δ = b2-4ac
Δ = 202-4·2·42
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-8}{2*2}=\frac{-28}{4}
=-7
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+8}{2*2}=\frac{-12}{4}
=-3
$