Inverses Modulo a Number
4 and 1/4 are inverses because 4* 1/4 = 1
In modulo world, want to find x such that
Also written a -1 = x (mod n)
Has unique solution if a and n are relatively prime.
If a and n aren’t relatively prime, has no solution.
4x = 1 (mod 7) <=> Finding x, k such that 4x = 7k + 1
Inverse of 5 modulo 14 = 3
2 has no inverse modulo 14.