250=1.2v+0.05v^2

Solution for 250=1.2v+0.05v^2 equation:

250=1.2v+0.05v^2

We move all terms to the left:

250-(1.2v+0.05v^2)=0

We get rid of parentheses

-0.05v^2-1.2v+250=0

a = -0.05; b = -1.2; c = +250;
Δ = b2-4ac
Δ = -1.22-4·(-0.05)·250
Δ = 51.44
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{-(-1.2)-\sqrt{51.44}}{2*-0.05}=\frac{1.2-\sqrt{51.44}}{-0.1}
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.2)+\sqrt{51.44}}{2*-0.05}=\frac{1.2+\sqrt{51.44}}{-0.1}
$