Group, Help Watch
Would any do question 1(vi) and 3(ii) and (iv)?
3ii) H_1 isn't a subgroup as what is the inverse of 1. H_2 is a subgroup - check the subgroup axioms.
3iv) H_1 is (recall that composition of maps is always associative), but H_2 isn't as the identity map wouldn't be in there.
3iv. H1 is a subgroup, H2 is not a subgroup since the identity does not exist (the identity being f(x)=x, which is clearly impossible if f(2)=0).