In: Advanced Math
For p a given prime number, define the p-adic norm | * |p as follows on Q: Given q in Q, we can write it as a product q = (p^m)(a/b) with a,b integers which are not divisible by p, and m an integer which is uniquely determined by q (check that m is indeed uniquely determined by q). Then define |q|p = p^(-m).
Check that Q with distance dp(q1,q2) = |q1 - q2|p is a metric
space (here q1-q2 just means the usual operation of subtraction in
Q). Show moreover
that |q1 + q2|p <= max(|q1|p, |q2|p).