A sequence is geometric if the ratio between any consecutive terms is the same. Each geometric sequence has a common ratio.

Example 1:Is the sequence 9, -18, 36, -72, … geometric? If so, state the recursive formula.

What is the 13th term of the sequence?

t1 =

t2 =

t3 =

...

tn = → t13 =

In general, if the first term of a sequence is a and the common ratio is r, then the nth term is given by the formula _______________.

Example 2:How many terms are in the geometric sequence 8748, 2916, 972, …, 12?

Example 3:A company has 3 kg of radioactive material that must be stored until it becomes environmentally safe. After one year, 95% of the radioactive material remains.How much radioactive material will be left after 100 years?

Geometric Sequences