Question

Counatable union of countable set is countable...​

Answer 1

Answer:

So given an element x in Z, we either have that 1↦x if x=0, 2x↦x if x>0, or 2|x|+1↦x if x<0. So the integers are countable. We proved this by finding a map between the integers and the natural numbers. So to show that the union of countably many sets is countable, we need to find a similar mapping.

Answer 2

babu..super..ma...

question lo enni early.. uncountable.. undo .