-3n^2-15n-12=0

Solution for -3n^2-15n-12=0 equation:

-3n^2-15n-12=0

a = -3; b = -15; c = -12;
Δ = b2-4ac
Δ = -152-4·(-3)·(-12)
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-9}{2*-3}=\frac{6}{-6}
=-1
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+9}{2*-3}=\frac{24}{-6}
=-4
$