In: Computer Science
The solution of this question is based upon Extended Euclidean Algorithm, we use it to find the multiplicative inverse of the number a
The first condition is that in a(mod b) variable 'a' and 'b' must be co primes.
Now we need to use this algorithm to find gcd of 'a' and 'b' and also find 'x' and 'y'. Such that
ax + by = gcd(a,b)
To find multiplicative inverse Of 'a' under 'm' Put b = m. Since a and m are relatively prime so gcd = 1.
=> ax + by = 1
Take modolu m on both sides
ax + my = 1(mod m)
my mod m value is always 0
ax = 1 ( mod m )
Here, x is the multiplicative inverse of 'a'.
so, value of 7^-1(mod 11) is 8.