How to solve this given equation(congruence)?












1












$begingroup$



Let $q^{'}mid q$ .



Let $yin U_{q^{'}}={x:gcd(x,q^{'})=1}$



Find a solution of the congruence $xequiv ymod q^{'}$ in $U_q={x:gcd(x,q)=1}$.




My try:



If $yin U_{q}$ then $x=y$ solves the equation.



If $ynotin U_{q}$ then after doing some examples I found $y+q^{'}$ solves the equation but I cant prove it.



Surely $y+q^{'}equiv ymod q^{'}$ but how to show that $gcd((y+q^{'}),q)=1$
if $gcd(y,q)neq 1$.



Any help to solve this equation?










share|cite|improve this question









$endgroup$












  • $begingroup$
    From the prime factorization of $q$ remove all primes that it shares with $y$. Call the resulting number $s$. Try $y+s$ as a solution.
    $endgroup$
    – Lozenges
    Jan 13 at 17:29
















1












$begingroup$



Let $q^{'}mid q$ .



Let $yin U_{q^{'}}={x:gcd(x,q^{'})=1}$



Find a solution of the congruence $xequiv ymod q^{'}$ in $U_q={x:gcd(x,q)=1}$.




My try:



If $yin U_{q}$ then $x=y$ solves the equation.



If $ynotin U_{q}$ then after doing some examples I found $y+q^{'}$ solves the equation but I cant prove it.



Surely $y+q^{'}equiv ymod q^{'}$ but how to show that $gcd((y+q^{'}),q)=1$
if $gcd(y,q)neq 1$.



Any help to solve this equation?










share|cite|improve this question









$endgroup$












  • $begingroup$
    From the prime factorization of $q$ remove all primes that it shares with $y$. Call the resulting number $s$. Try $y+s$ as a solution.
    $endgroup$
    – Lozenges
    Jan 13 at 17:29














1












1








1





$begingroup$



Let $q^{'}mid q$ .



Let $yin U_{q^{'}}={x:gcd(x,q^{'})=1}$



Find a solution of the congruence $xequiv ymod q^{'}$ in $U_q={x:gcd(x,q)=1}$.




My try:



If $yin U_{q}$ then $x=y$ solves the equation.



If $ynotin U_{q}$ then after doing some examples I found $y+q^{'}$ solves the equation but I cant prove it.



Surely $y+q^{'}equiv ymod q^{'}$ but how to show that $gcd((y+q^{'}),q)=1$
if $gcd(y,q)neq 1$.



Any help to solve this equation?










share|cite|improve this question









$endgroup$





Let $q^{'}mid q$ .



Let $yin U_{q^{'}}={x:gcd(x,q^{'})=1}$



Find a solution of the congruence $xequiv ymod q^{'}$ in $U_q={x:gcd(x,q)=1}$.




My try:



If $yin U_{q}$ then $x=y$ solves the equation.



If $ynotin U_{q}$ then after doing some examples I found $y+q^{'}$ solves the equation but I cant prove it.



Surely $y+q^{'}equiv ymod q^{'}$ but how to show that $gcd((y+q^{'}),q)=1$
if $gcd(y,q)neq 1$.



Any help to solve this equation?







abstract-algebra group-theory elementary-number-theory modular-arithmetic






share|cite|improve this question













share|cite|improve this question











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asked Jan 13 at 6:55







user596656



















  • $begingroup$
    From the prime factorization of $q$ remove all primes that it shares with $y$. Call the resulting number $s$. Try $y+s$ as a solution.
    $endgroup$
    – Lozenges
    Jan 13 at 17:29


















  • $begingroup$
    From the prime factorization of $q$ remove all primes that it shares with $y$. Call the resulting number $s$. Try $y+s$ as a solution.
    $endgroup$
    – Lozenges
    Jan 13 at 17:29
















$begingroup$
From the prime factorization of $q$ remove all primes that it shares with $y$. Call the resulting number $s$. Try $y+s$ as a solution.
$endgroup$
– Lozenges
Jan 13 at 17:29




$begingroup$
From the prime factorization of $q$ remove all primes that it shares with $y$. Call the resulting number $s$. Try $y+s$ as a solution.
$endgroup$
– Lozenges
Jan 13 at 17:29










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