Question

If n(x)=4 & n(y)=5, find maximum value of n(xuy)

Answer 1

n(xuy)=n(x)+n(y)-n(xny)
n(xuy)=4+5-n(xny)
n(xuy)=9-n(xny)
since,
n(xny) can't be negative can be 0 or positive integer
therefore,
maximum value of n(xuy) is 9