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Math Help - Confusion regarding symbol

  1. #1
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    Confusion regarding symbol

    Hey guys , i am unclear regarding a symbol which i encountered in my work. I was given a question in which they state a few algorithm. The part which i am confused about is when they told me to use a variable named q where q|P -1 . P is also a variable , but a prime number.

    What i am confused about is what does "|" mean?

    1) Does it mean that q = P -1 , which means to say if P is 11 , q is 10?

    2) Does it mean that q can be any number which is less then P -1 ? If P = 11 , then q can be from 1 till 10.


    Or am i completely wrong in understanding what "|" does? Hope for some clarification. Thank you.
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  2. #2
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    \displaystyle q|P-1 \ \mbox{means} \ q*x=P-1

    This should help you answer both your questions.
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  3. #3
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    Hey , thank for the reply. Im not sure if i understand what u mean , but let me try explaining to you what i see and hope you can tell me if i am right.

    Basically , when q * x , the value of it is suppose to be P - 1? What is x and how do we go about to get it?
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  4. #4
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    q|(p-1) reads "q divides p-1".
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  5. #5
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    x\in\mathbb{Z}

    Looking at your example of p=11 we get x by:

    q*x=11-1\rightarrow q*x=10 \ \mbox{and since q is prime} \ q=2,5\rightarrow 2*x=10 \ \mbox{or} \ 5*x=10 Thus, x = 5 or 2
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  6. #6
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    okay , so what i means that the value of q is based on the value of (p - 1)?

    So , for example if p = 11 , then q should be 10 as 10|(p - 1) = 1?
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  7. #7
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    q is prime so q isn't 10 but q*x=10 where q can be 2 or 5 which are prime numbers.
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  8. #8
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    Quote Originally Posted by gregarion View Post
    10|(p - 1) = 1?
    This shouldn't have an equal sign.

    10|(p-1)\rightarrow 10*x=p-1 The equal sign is built into the divides notation.
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  9. #9
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    Okay , q always has to be a prime? Let me see if i get it .

    P = 281
    q|(P-1) = 280

    Factors of 280 = 2 * 2 * 2 * 5 * 7

    Thus , q can be either 2, 5 or 7?

    Sorry , 10|(p - 1) = 1 was suppose to mean that when 10 is divided by (p-1) , the value should be 1.
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  10. #10
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    I miss read your sentence. q doesn't have to be prime. But you seem to have figured out how to solve it now. Just pick a q*x which equals P-1.
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  11. #11
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    okay , so if q is not a prime , then when P = 280 and q is based on q|P-1 , thus q can be 280 then? as it fulfills the requirement of it having to be equals P -1.
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  12. #12
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    Yup. Then x=1.
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  13. #13
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    Thanks a lot for the clarification !
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