- #1
annoymage
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Homework Statement
Let gcd(h,k)=1, o(a)=h, o(b)=k, show that o(ab)=hk
Homework Equations
o(a)= order of a modulo n
o(a)=k iff k is smallest integer,[itex] a^k=1 mod n[/itex]
The Attempt at a Solution
to prove o(ab) l hk, no problem, just need to show [itex](ab)^{hk}=1 mod n[/itex]
and to prove hk l o(ab), use division algorithm
let, hk=p*o(ab)+q , [itex]0\leq q<p[/itex]
it can be shown that [itex](ab)^q=1 mod n[/itex], this will imply q=0, so o(ab) l hk
and i really think i didn't make any mistake, but i didn't use that gcd(h,k)=1.
can help me anywhere i wrong? or is this gcd(h,k)=1 is unnecessary?
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