Section 9.3 Geometric Sequences

The difference between arithmetic and geometric sequences is that arithemtic sequences has a common difference in each sequence, whereas a geometric sequence has a Common Ratio.

It is a geometric sequence if the ratios of consecutive terms are the same.

 =  .....= r.  r  0


The common ratio here is 2 because as you can see each number multiplied by 2 gives you the next term.

When solving for a certain term or the nth term of a sequence, you would use the equation:

Always remember that r is the common ratio of consecutive terms of a geometric sequence.

A very important equation to remember is The Sum of a Finite Geometric Sequence

The other very important equation to remember from this chapter is the Sum of an Infinite Geometric Series. This equation is very similar to that of the sum of finite geometric sequences. This equation is to be used when r, the common ratio, is less than 0.

This section could not have been learned without the help of the great math teacher: Thad Wilhelm.