Prove that if X is countable and a is in X then X \{a} is countable.

issacnewton

A subset of countable set is countable. Since
[tex]X\setminus\{a\}\subseteq X[/tex]

we have that [itex]X\setminus\{a\}[/itex] is countable. So try proving first that any subset of a countable set is countable

issacnewton	A subset of countable set is countable. Since [tex]X\setminus\{a\}\subseteq X[/tex] we have that [itex]X\setminus\{a\}[/itex] is countable. So try proving first that any subset of a countable set is countable