A geometric sequence has a constant ratio (common ratio) between consecutive terms.

For 3, 9, 27, … the common ratio is 3 because: 3 X 3 = 9 9 X 3 = 27

So to find the 7th term you can do it two ways:

One way: 3 is the 1st term, 9 is the 2nd term, 27 is the 3rd term so then 4th term: 27 X 3 = 81 5th term: 81 X 3 = 243 6th term: 243 X 3 = 729 7th term: 729 X 3 = 2,187

Another way: You can use the explicit formula ##a_n = a_1 *r^(n-1)##, where ##a_n## is the nth term, ##a_1## is the first term, n is the number of the term, and r is the common ratio

so ##a_7 = 3 * 3^ (7-1)## ##a_7 = 3 * 3^ (6)## ##a_7 = 3 * 729## ##a_7 = 2,187##

Both ways get you to the same answer that the 7th term in that geometric sequence is 2, 187 .