Pls help!!

Jake has proved that a function, f(x), is a geometric sequence. How did he prove that? (1 point)
He showed that an explicit formula could be created.
He showed that a recursive formula could be created.
He showed that f(n) รท f(n โˆ’ 1) was a constant ratio.
He showed that f(n) โˆ’ f(n โˆ’ 1) was a constant difference.