Geometric Sequences and Series

Arithmetic Sequences ADD To get next term Geometric Sequences MULTIPLY To get next term Arithmetic Series Sum of Terms Geometric Series Sum of Terms 2. Geometric Sequences and Series a1a1 a2a2 a3a3 a4a4 a5a5 a6a6 anan a n d  r r  r r  r r  r r  r r  r r

Geometric Sequences (Type 2) In geometric sequences, you multiply by a common ratio (r) each time. 1, 2, 4, 8, 16,... multiply by 2 27, 9, 3, 1, 1/3,... Divide by 3 which means multiply by 1/3 ie

The nth term of an geometric sequence is denoted by the formula Where a is the 1 st term and r is the common ratio The sum of the first n terms of a geometric series is found by using: Note if r>1 then we can use the formula Which is more convenient

Vocabulary of Sequences (Universal)

Find the next three terms of 2, 3, 9/2, ___, ___, ___ 3 – 2 vs. 9/2 – 3… not arithmetic

1/2 x 9 NA 2/3

Example 2 Find u 10 for the geometric sequence 144, 108, 81, 60¾, … Answer u 1 = 144 and r = u 10 = ar n-1 = 144 (¾) 9 = …

Example 3 Find S 19 for the geometric sequence … Answer U 1 = 3 and r =

-3, ____, ____, ____

The Bouncing Ball Problem – Version A A ball is dropped from a height of 50 feet. It rebounds 4/5 of it’s height, and continues this pattern until it stops. How far does the ball travel? / /5

The Bouncing Ball Problem – Version B A ball is thrown 100 feet into the air. It rebounds 3/4 of it’s height, and continues this pattern until it stops. How far does the ball travel? / /4

An old grandfather clock is broken. When the pendulum is swung it follows a swing pattern of 25 cm, 20 cm, 16 cm, and so on until it comes to rest. What is the total distance the pendulum swings before coming to rest?