For a variable x, we have (where a1 is just the first answer box and a2 is the second answer box)
$$(x+1)^n = \sum_{k=0}^n \binom{n}{k}(a_1)^{a_2}$$
what does $a_1$ and $a_2$ equal? I'm not even entirely sure I understand all of the notation, or what is happening to the $(x+1)^n$
I tried to just think about how to write that equation as a summation, and ended up thinking that $a_1 = x + 1$ and $a_2 = k$, just because n would be replaced by k, starting from 0 all the way up to n, but I really have no idea.