Q.

For non-negative integers s and r, let

(sr)={s!r!(s-r)!if rs,0if r>s.

For positive integers m and n, let

g(m,n)=p=0m+nf(m,n,p)(n+pp)

where for any non-negative integer p,

f(m,n,p)=i=0p(mi)(n+ip)(p+np-i).

Then which of the following statements is/are TRUE                [2020]

1 g(m,n)=g(n,m)  for all positive integers m,n,  
2 g(m,n+1)=g(m+1,n)  for all positive integers m,n  
3 g(2m,2n)=2g(m,n)  for all positive integers m,n  
4 g(2m,2n)=(g(m,n))2  for all positive integers m,n  

Ans.

(1, 2, 4)

So, options (1), (2) and (4) are true.