-80=-72n-56n2

Solution for -80=-72n-56n2 equation:

-80=-72n-56n^2

We move all terms to the left:

-80-(-72n-56n^2)=0

We get rid of parentheses

56n^2+72n-80=0

a = 56; b = 72; c = -80;
Δ = b2-4ac
Δ = 722-4·56·(-80)
Δ = 23104
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{23104}=152$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-152}{2*56}=\frac{-224}{112}
=-2
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+152}{2*56}=\frac{80}{112}
=5/7
$