Homework Statement
\forall x\in Z, if x is odd, \exists y\in Z, such that xy\equiv1(mod 16)
The attempt at a solution
I tried to prove this by using the fact that if you got a set of odd integers R = {1, 3, 5, ..., 15}, and if x, y, f(r) \in R, then xy\equiv f(r)(mod 16). This...