## Calculus (3rd Edition)

(a) We have two different bases and can not put them together. Thus, there is no match. (b) Since $\frac{2^a}{3^{b}}=2^a3^{-b}$, then for (b) there is no match. (c) We can multiply the exponents to match (i). (d) Note that $b-a=-(a-b)$ Thus we have: $2^{a-b}3^{-(a-b)}$, which matches (iii).