Answer :
Based on your question the possible answer would be
a) set of all (u.v) such that u and v are ratios of p/q of integers.
b) set of all (u.v) where u=0 or v=0.
How can these vectors be closed for one and not closed for the other operation??
a) set of all (u.v) such that u and v are ratios of p/q of integers.
b) set of all (u.v) where u=0 or v=0.
How can these vectors be closed for one and not closed for the other operation??