In Exercises 17–24, write a formula for the general term (the nth term) of each geometric sequence. Then use the formula for a_n to find a7, the seventh term of the sequence.18, 6, 2, 2/3, ...

A geometric sequence is a sequence of numbers where each term after the first is found by multiplying the previous term by a fixed, non-zero number called the common ratio. For example, in the sequence 18, 6, 2, 2/3, the common ratio can be found by dividing any term by its preceding term, which in this case is 1/3.

The general term (nth term) of a geometric sequence can be expressed using the formula a_n = a_1 * r^(n-1), where a_1 is the first term, r is the common ratio, and n is the term number. This formula allows us to calculate any term in the sequence without having to list all previous terms.

To find a specific term in a geometric sequence, such as a7, we substitute n with 7 in the general term formula. By calculating a7 using the identified first term and common ratio, we can determine the value of the seventh term in the sequence, which is essential for understanding the behavior of the sequence.