280=3n^2-17n

Solution for 280=3n^2-17n equation:

280=3n^2-17n

We move all terms to the left:

280-(3n^2-17n)=0

We get rid of parentheses

-3n^2+17n+280=0

a = -3; b = 17; c = +280;
Δ = b2-4ac
Δ = 172-4·(-3)·280
Δ = 3649
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-\sqrt{3649}}{2*-3}=\frac{-17-\sqrt{3649}}{-6}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+\sqrt{3649}}{2*-3}=\frac{-17+\sqrt{3649}}{-6}
$