v2-6v=20

Solution for v2-6v=20 equation:

v2-6v=20

We move all terms to the left:

v2-6v-(20)=0

We add all the numbers together, and all the variables

v^2-6v-20=0

a = 1; b = -6; c = -20;
Δ = b2-4ac
Δ = -62-4·1·(-20)
Δ = 116
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:

$\sqrt{\Delta}=\sqrt{116}=\sqrt{4*29}=\sqrt{4}*\sqrt{29}=2\sqrt{29}$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-2\sqrt{29}}{2*1}=\frac{6-2\sqrt{29}}{2}
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+2\sqrt{29}}{2*1}=\frac{6+2\sqrt{29}}{2}
$