Butch Malahide wrote: > On Tuesday, July 9, 2013 5:39:00 AM UTC-5, Sandy wrote: >> For n, m natural numbers, n < m, let G be the free group on n generators and H the free group on m generators. Is H an elementary extension of G? > > I guess you meant to say that n > 1.
Indeed I did! (And I thought I'd acknowledged that elsewhere, but the post, and the post I was replying to, have disappeared. Perhaps I dreamt it.) Btw, I have since found that this is problem 3 at the back of Chang & Keisler's /Model Theory/. I have the second edition, maybe subsequent editions solve it or at least give reference to its solution