Answer:

Firstly, f (n) = N4-360N2+400 = (N2+20) 2-(20n) 2 = (N2-20n+20) (N2+20n+20); Since f(n) is a prime number and n is a positive integer, there must be n 2-20N+20 =1,and the solution is n= 1 or n= 19. If you bring it in, you will get f(n) equal to 4 1 and 76/kloc-respectively.