F# Seq diff

given two sequences, how to get all the elements belonging to both the sequences or all the elements unique to one of them?

Example:

let a = [1..10]
let b = [3; 5; 7]

How do I compute 3 5 and 7 (all the elements common to both the list) and 1, 2, 4, 6, 8, 9, 10 (all the elements not in common)

Thanks