Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

modular arithmetic watch

Announcements
    • Thread Starter
    Offline

    2
    ReputationRep:
    how come u can cancel multiples if u r using a prime base...but not if u r using a composite one...e.g

    ax=ay (mod p) where p is prime
    then x=y (mod p)

    but u could not do that if p were not prime??? why?
    • Thread Starter
    Offline

    2
    ReputationRep:
    also can u say that for example 13=11 (mod 2)??
    Offline

    1
    ReputationRep:
    Because if it is prime, and u have
    ab = 0 (mod p)
    Then either a = 0 (mod p), or b = 0 (mod p)

    For composite numbers, it doesnt work like that, for instance

    2*4 = 0 (mod 8)
    but neither 2 or 4 = 0 (mod 8).


    The definition of a prime number is: if p is prime, then
    p|ab implies p|a or p|b.
    Offline

    1
    ReputationRep:
    Also, if u have p is composite, then

    ax = ay (mod p)
    x = y (mod p) is only true if a and p are coprime.

    Anyway, ive gotta go, bye.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by JamesF)
    Also, if u have p is composite, then

    ax = ay (mod p)
    x = y (mod p) is only true if a and p are coprime.

    Anyway, ive gotta go, bye.
    so it can be possible if p is not prime as long as p is not a multiple of a?
    is it a definition of modulra arithmetic that p is bigger than a????
 
 
 
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.