Question about congruences.

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  1. canine101's Avatar
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    • Location: London
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    Question about congruences.
    I have a question which says

     9x^2 = 5mod11

    (just assume the equals sign is a congruence one). I know how to do these without a coefficient however I'm not sure what difference is made with the presence of one. This might be a really simple question but I'm confused about it so thought I'd ask anyway. Any help would really be appreciated.
  2. Mr M's Avatar
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    Re: Question about congruences.
    (Original post by canine101)
    I have a question which says

     9x^2 = 5mod11

    (just assume the equals sign is a congruence one). I know how to do these without a coefficient however I'm not sure what difference is made with the presence of one. This might be a really simple question but I'm confused about it so thought I'd ask anyway. Any help would really be appreciated.
    To solve ax^2 = b mod c multiply by a' where aa'=1 mod c.

    You obtain x^2 =ba' mod c which you know how to solve.
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