abstract algebra?

Question

is U(30)/U_5(30) isomorphic to Z_2 + Z_2
orZ_4
plzzzzzzzzzz explain

U_k(n)={x belong to U_n I xmod k =1}
where k is adivisor of n
G/H is afactor group
is it clear???

Answer 1

Let G = U(30) = {1,7,11,13,17,19,23,29} and

H=U_5(30) = {1,11}.

Then (7*H)^2 = 19*H. So its order is 4, not 2. So the group is Z_4.

Answer 2

:(...you explain your question...