(a) let h and k be two subgroups of a commutative group g. suppose that |h| = m and |k| =n. let d = lcm(m, n). show that g has a subgroup of order d.

(C*,x) be a commutative group H = cubic root of unity is a subgroup of order 3 K is 4th root of unity is subgroup of unity d=LCM(3,4)=12 12th root of unity is subgroup of unity ...