13-1 Arithmetic and Geometric Sequences

This weekend I am going to teach you all about arithmetic and geometric sequences. These are patterns that you have to do different things with. Sometimes they will ask you for a certain term number and other times they will ask you for a formula. There are some things that you need to know about arithmetic and geometric sequences before I show you all an example.

Notes:

• Arithmetic Sequences
o They are generated when the same number is added every time
o The formula for this type of sequence is tn = t1 + (n-1) * d
o d= what is being added, or the difference
o tn= ___ term
o t1= 1st term
o n= term number

• Geometric Sequences
o They are generated when the same number is multiplied every time
o The formula for this type of sequence is tn = t1 + r^(n-1)
o You cannot divide, so you have to multiply by fractions
o r = what is being multiplied

Example: tn= 2n + 5; find the first four terms and state whether the sequence is arithmetic or geometric
• 2 (1) + 5 = 7
• 2 (2) + 5 = 9
• 2 (3) + 5 = 11
• 2 (4) + 5 = 13
• 7, 9, 11, 13,…..
• This sequence is arithmetic; +2

-Braxton