V(t)=5t^2-20t+20

Solution for V(t)=5t^2-20t+20 equation:

(V)=5V^2-20V+20

We move all terms to the left:

(V)-(5V^2-20V+20)=0

We get rid of parentheses

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

We add all the numbers together, and all the variables

-5V^2+21V-20=0

a = -5; b = 21; c = -20;
Δ = b2-4ac
Δ = 212-4·(-5)·(-20)
Δ = 41
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$V_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$V_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$V_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-\sqrt{41}}{2*-5}=\frac{-21-\sqrt{41}}{-10}
$
$V_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{41}}{2*-5}=\frac{-21+\sqrt{41}}{-10}
$