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issacnewton
issacnewton is offline
#3
Mar8-12, 10:38 PM
P: 606
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