Ive been having issues with a question on my assignment:
Determine whether each of these sets is countable or uncountable. For those that are countably infinite,
exhibit a one-to-one correspondence between the set of positive integers and that set.
- integers not divisible by 3
- integers divisible by 5 but not by 7
- the real numbers with decimal representations consisting of all 1s
- the real numbers with decimal representations of all 1s or 9s