Answer:
The empirical formula will be AB₃.
Explanation:
In chemistry the empirical formula is an expression that represents the simplest proportion in which the atoms that form a chemical compound are present. It is therefore the simplest representation of a compound.
In this example the compound A₃B₉ has 3 atoms of A and 9 atoms of B.
The simplest positive integer ratio of atoms of the compound will be 1:3 (1 atom of A and 3 atoms of B). In other words we have to divide by 3 each subindex of the compound.
