I am trying to do exercise n.6 on page 229 of "A Course in Universal Algebra" by S.Burris & H.P.Sankappanavar:
"Show that 'being of infinite size' is a first-order property (relative to any K)".
I understand that there must be a first order formula expressing 'being of infinite size', but I do not know how to find it.
Would anybody help me ?
Thank you very much
Am I right if I say:
s(x) means successor of x
then (see attachment)