-(12n^2+11n-15)=0

Solution for -(12n^2+11n-15)=0 equation:

-(12n^2+11n-15)=0

We get rid of parentheses

-12n^2-11n+15=0

a = -12; b = -11; c = +15;
Δ = b2-4ac
Δ = -112-4·(-12)·15
Δ = 841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{841}=29$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-11)-29}{2*-12}=\frac{-18}{-24}
=3/4
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+29}{2*-12}=\frac{40}{-24}
=-1+2/3
$