I am oh so confused about how to prove things as countable or uncountable. Mainly the former.
We learned about it in lecture but I'm still lost.
Could someone explain how you'd say something is countable in an example like:
- Let's consider disks, 2d regions of the form ${(x, y) ∈ R^2 : (x−x_{0})^2 + (y−y_{0})^2 ≤ r^2}$ such that $x_{0}, y_{0}, r ∈ R$ . Say you have a set of disks none of which overlap. Is the set countable or could it be uncountable?