Using "The Quadratic Trinomial" when I factor a -1 out of 15 - n(2) + 2n

What is the extention of this? I'm not really sure if what I have is correct and I need someone elses opinion.
(BTW: in 15 - n(2) +2n
the n(2) is n squared)

by the way to show a squared number online just press shift and 6 at the same time to get ^ to write n^2

and im not quite sure what you are asking but if you factoe -1 out of 15-n^2+2n you get
-1(n^2 - 2n - 15)

so now you can use the quadratic formula with a=1 b=-2 and c=-15 to solve for n

15 - n(2) + 2n = 15 - n² + 2n = (-1)[-15 + n² - 2n]

n² ≥ 0 if n is a real number.
-n² ≤ 0 if n is a real number. [Real numbers are complex numbers that have a zero imaginary component.]