So here is this question I got stuck on:
Let $(a,b)$, $(c,d)$ be intervals (not sure if that's the correct term) on $\Bbb R$, so that $a<b$, $c<d$. Find an injective and surjective function $f:(a,b)\rightarrow(c,d)$.
Thanks in advance!
P.S. I get these question a lot. Is that some way of thinking, or some general method I should follow to make these question easier for me to solve?