40n^2-285n-280=0

Solution for 40n^2-285n-280=0 equation:

40n^2-285n-280=0

a = 40; b = -285; c = -280;
Δ = b2-4ac
Δ = -2852-4·40·(-280)
Δ = 126025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{126025}=355$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-285)-355}{2*40}=\frac{-70}{80}
=-7/8
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-285)+355}{2*40}=\frac{640}{80}
=8
$