-n^2+9n+36=0

Solution for -n^2+9n+36=0 equation:

-n^2+9n+36=0

We add all the numbers together, and all the variables

-1n^2+9n+36=0

a = -1; b = 9; c = +36;
Δ = b2-4ac
Δ = 92-4·(-1)·36
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-15}{2*-1}=\frac{-24}{-2}
=+12
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+15}{2*-1}=\frac{6}{-2}
=-3
$