Doubt in little fermat theoram to find inverse?

#1

If i want to find the inverse of 15 with respect 4
then
a^(p-2) mod p will give me the answer
15^2 = 225
and 225 % 4 = 1
but (15*1) % 4 = 3 and not 1 hence 1 is not the answer
How?

#2

hello @deepak_four there is condition in the litte fermats theore that a^(p-1)%p=1 only when p is a prime number ,
and in your query 4 is not the prime number.
Happy Learning !!

#3

Okay,
So to find the multiplicative inverse we need to use the euclid approach, Is there any other way?

#4

Yes euclid approach.
the another approach will be the brute force approach.
if you feel that your doubt is cleared please mark this doubt as resolved.
Happy Learning!!

#5

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