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$((p-1)/2)!^2$ congruent $-(-1)^{(p-1)/2} mod p$


how to solve $ax+by=c mod p$?Differences Between Multiples of Consecutive Odd PrimesProve or disprove: For every integer a, if a is not congruent to 0 (mod 3), the a^2 is congruent to 1 (mod 3)Prove that there is no perfect square that is congruent to 2 mod 10 and 3 mod 10.How to prove that $(a-b) mod N = a mod N + ((-b) mod N)$?What is a modular inverse?Ian Stewart difference between two real numbers with the same decimal expansion to n placesFind the smallest positive integer for which x mod 3 = 2 and x mod 4 = 3If a = b (mod m) and gcd(a,b) = 1, then gcd(a,m) = 1Efficient way to solve $31^6 mod 189$ without using any external devices.













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I have run across a similar question in several places and the difference between the similar question and my question is that there is a negative sign next to $(-1)^{(p-1)/2}$. I am trying to figure out how the proof of these two differ.










share|cite|improve this question











$endgroup$












  • $begingroup$
    Wilson's theorem?
    $endgroup$
    – Lord Shark the Unknown
    yesterday










  • $begingroup$
    Yes you can use Wilsons to get it down to -1 congruent (-1)^((p-1)/2)((p-1)/2)!^2 mod p but I am unsure how to get to final answer from there.
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Also if anyone could upvote my question so I can actually comment on other posts that would be great
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Did you want the factorial symbol outside the parentheses in the title?
    $endgroup$
    – J. W. Tanner
    yesterday










  • $begingroup$
    Hint $, $ If $,a^{large 2}equiv 1,$ then $ axequiv {-}1 iff xequiv -a $ (by multiplying by $a). $ OP has $, aequiv (-1)^{large (p-1)/2}pmod{!p}$
    $endgroup$
    – Bill Dubuque
    yesterday


















1












$begingroup$


I have run across a similar question in several places and the difference between the similar question and my question is that there is a negative sign next to $(-1)^{(p-1)/2}$. I am trying to figure out how the proof of these two differ.










share|cite|improve this question











$endgroup$












  • $begingroup$
    Wilson's theorem?
    $endgroup$
    – Lord Shark the Unknown
    yesterday










  • $begingroup$
    Yes you can use Wilsons to get it down to -1 congruent (-1)^((p-1)/2)((p-1)/2)!^2 mod p but I am unsure how to get to final answer from there.
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Also if anyone could upvote my question so I can actually comment on other posts that would be great
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Did you want the factorial symbol outside the parentheses in the title?
    $endgroup$
    – J. W. Tanner
    yesterday










  • $begingroup$
    Hint $, $ If $,a^{large 2}equiv 1,$ then $ axequiv {-}1 iff xequiv -a $ (by multiplying by $a). $ OP has $, aequiv (-1)^{large (p-1)/2}pmod{!p}$
    $endgroup$
    – Bill Dubuque
    yesterday
















1












1








1





$begingroup$


I have run across a similar question in several places and the difference between the similar question and my question is that there is a negative sign next to $(-1)^{(p-1)/2}$. I am trying to figure out how the proof of these two differ.










share|cite|improve this question











$endgroup$




I have run across a similar question in several places and the difference between the similar question and my question is that there is a negative sign next to $(-1)^{(p-1)/2}$. I am trying to figure out how the proof of these two differ.







elementary-number-theory modular-arithmetic






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited yesterday







redneckmathematician

















asked yesterday









redneckmathematicianredneckmathematician

124




124












  • $begingroup$
    Wilson's theorem?
    $endgroup$
    – Lord Shark the Unknown
    yesterday










  • $begingroup$
    Yes you can use Wilsons to get it down to -1 congruent (-1)^((p-1)/2)((p-1)/2)!^2 mod p but I am unsure how to get to final answer from there.
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Also if anyone could upvote my question so I can actually comment on other posts that would be great
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Did you want the factorial symbol outside the parentheses in the title?
    $endgroup$
    – J. W. Tanner
    yesterday










  • $begingroup$
    Hint $, $ If $,a^{large 2}equiv 1,$ then $ axequiv {-}1 iff xequiv -a $ (by multiplying by $a). $ OP has $, aequiv (-1)^{large (p-1)/2}pmod{!p}$
    $endgroup$
    – Bill Dubuque
    yesterday




















  • $begingroup$
    Wilson's theorem?
    $endgroup$
    – Lord Shark the Unknown
    yesterday










  • $begingroup$
    Yes you can use Wilsons to get it down to -1 congruent (-1)^((p-1)/2)((p-1)/2)!^2 mod p but I am unsure how to get to final answer from there.
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Also if anyone could upvote my question so I can actually comment on other posts that would be great
    $endgroup$
    – redneckmathematician
    yesterday










  • $begingroup$
    Did you want the factorial symbol outside the parentheses in the title?
    $endgroup$
    – J. W. Tanner
    yesterday










  • $begingroup$
    Hint $, $ If $,a^{large 2}equiv 1,$ then $ axequiv {-}1 iff xequiv -a $ (by multiplying by $a). $ OP has $, aequiv (-1)^{large (p-1)/2}pmod{!p}$
    $endgroup$
    – Bill Dubuque
    yesterday


















$begingroup$
Wilson's theorem?
$endgroup$
– Lord Shark the Unknown
yesterday




$begingroup$
Wilson's theorem?
$endgroup$
– Lord Shark the Unknown
yesterday












$begingroup$
Yes you can use Wilsons to get it down to -1 congruent (-1)^((p-1)/2)((p-1)/2)!^2 mod p but I am unsure how to get to final answer from there.
$endgroup$
– redneckmathematician
yesterday




$begingroup$
Yes you can use Wilsons to get it down to -1 congruent (-1)^((p-1)/2)((p-1)/2)!^2 mod p but I am unsure how to get to final answer from there.
$endgroup$
– redneckmathematician
yesterday












$begingroup$
Also if anyone could upvote my question so I can actually comment on other posts that would be great
$endgroup$
– redneckmathematician
yesterday




$begingroup$
Also if anyone could upvote my question so I can actually comment on other posts that would be great
$endgroup$
– redneckmathematician
yesterday












$begingroup$
Did you want the factorial symbol outside the parentheses in the title?
$endgroup$
– J. W. Tanner
yesterday




$begingroup$
Did you want the factorial symbol outside the parentheses in the title?
$endgroup$
– J. W. Tanner
yesterday












$begingroup$
Hint $, $ If $,a^{large 2}equiv 1,$ then $ axequiv {-}1 iff xequiv -a $ (by multiplying by $a). $ OP has $, aequiv (-1)^{large (p-1)/2}pmod{!p}$
$endgroup$
– Bill Dubuque
yesterday






$begingroup$
Hint $, $ If $,a^{large 2}equiv 1,$ then $ axequiv {-}1 iff xequiv -a $ (by multiplying by $a). $ OP has $, aequiv (-1)^{large (p-1)/2}pmod{!p}$
$endgroup$
– Bill Dubuque
yesterday












1 Answer
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0












$begingroup$

You said in the comments you use Wilson's theorem to show $$-1 equiv (-1)^{left(p-1right)/2}(frac {p-1} 2)!^2 pmod p,$$ and you want to show $$ -(-1)^{(p-1)/2}equivleft(frac {p-1} 2 right)!^2pmod p; ?$$



Multiply both sides by $(-1)^{(p-1)/2}$



and note that $ (-1)^{(p-1)/2} (-1)^{(p-1)/2}=(-1)^{p-1} = 1$ when $p$ is odd.






share|cite|improve this answer









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    1 Answer
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    0












    $begingroup$

    You said in the comments you use Wilson's theorem to show $$-1 equiv (-1)^{left(p-1right)/2}(frac {p-1} 2)!^2 pmod p,$$ and you want to show $$ -(-1)^{(p-1)/2}equivleft(frac {p-1} 2 right)!^2pmod p; ?$$



    Multiply both sides by $(-1)^{(p-1)/2}$



    and note that $ (-1)^{(p-1)/2} (-1)^{(p-1)/2}=(-1)^{p-1} = 1$ when $p$ is odd.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      You said in the comments you use Wilson's theorem to show $$-1 equiv (-1)^{left(p-1right)/2}(frac {p-1} 2)!^2 pmod p,$$ and you want to show $$ -(-1)^{(p-1)/2}equivleft(frac {p-1} 2 right)!^2pmod p; ?$$



      Multiply both sides by $(-1)^{(p-1)/2}$



      and note that $ (-1)^{(p-1)/2} (-1)^{(p-1)/2}=(-1)^{p-1} = 1$ when $p$ is odd.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        You said in the comments you use Wilson's theorem to show $$-1 equiv (-1)^{left(p-1right)/2}(frac {p-1} 2)!^2 pmod p,$$ and you want to show $$ -(-1)^{(p-1)/2}equivleft(frac {p-1} 2 right)!^2pmod p; ?$$



        Multiply both sides by $(-1)^{(p-1)/2}$



        and note that $ (-1)^{(p-1)/2} (-1)^{(p-1)/2}=(-1)^{p-1} = 1$ when $p$ is odd.






        share|cite|improve this answer









        $endgroup$



        You said in the comments you use Wilson's theorem to show $$-1 equiv (-1)^{left(p-1right)/2}(frac {p-1} 2)!^2 pmod p,$$ and you want to show $$ -(-1)^{(p-1)/2}equivleft(frac {p-1} 2 right)!^2pmod p; ?$$



        Multiply both sides by $(-1)^{(p-1)/2}$



        and note that $ (-1)^{(p-1)/2} (-1)^{(p-1)/2}=(-1)^{p-1} = 1$ when $p$ is odd.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered yesterday









        J. W. TannerJ. W. Tanner

        2,9271217




        2,9271217






























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