0=v^2+4v-66

Solution for 0=v^2+4v-66 equation:

0=v^2+4v-66

We move all terms to the left:

0-(v^2+4v-66)=0

We add all the numbers together, and all the variables

-(v^2+4v-66)=0

We get rid of parentheses

-v^2-4v+66=0

We add all the numbers together, and all the variables

-1v^2-4v+66=0

a = -1; b = -4; c = +66;
Δ = b2-4ac
Δ = -42-4·(-1)·66
Δ = 280
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{280}=\sqrt{4*70}=\sqrt{4}*\sqrt{70}=2\sqrt{70}$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-2\sqrt{70}}{2*-1}=\frac{4-2\sqrt{70}}{-2}
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+2\sqrt{70}}{2*-1}=\frac{4+2\sqrt{70}}{-2}
$