Just explain, i know the anwser

You have to use Newton-Raphson iteration method. You may have to look it up.
y =- 6 and n = - 4
y = 2 and n = - 4
y = - 6 and n = - 2
y = 4  and  n = - 2
y = 2  and  n = 6
y = 4  and  n = 6

First divide both sides by 2.

\(ny^2=n^2y-48\)

Then move all the variables to one side.

\(n^2y-ny^2=48\)

\(ny(n-y)=48\)

I factorized 48 and used trial and error to find

\(ny=12\)

\(n-y=4\)

Solve and find \(n=6, y=2\)

With your problem, the factoring can result in more than one correct answer, but the process shown is good.

The "Newton-Raphson iteration method" has nothing to do with this problem.