Answer
Done below.
Work Step by Step
a) Each $A_i$ is contained in the next $A_{i+1}$. Hence the union is just the final term $A_n = \{\cdots, -2, -1, 0, 1, \cdots, n\}$.
b) The only terms contained in all of the $A_i$ are $\cdots, -2, -1, 0, 1$. Hence the intersection is $\{\cdots, -2, -1, 0, 1\}$, i.e. $A_1$.
