Arithmetic Series &

Geometric Series

--- SusanDerek

Arithmetic Series

1, 4, 7, 10, 13, 16 …

3, 8, 13, 18, 23, 28…

So the Nth number is :

an = a1 + d(n-1)

dd --- difference --- use the 2nd number minus the first number

Geometric Series

1, 2, 4, 8, 16, 32…

1, 10, 100, 1000, 10000…

So the Nth number is:

an = a1 r^n-1

r --- ratio --- use the 2nd number divde the first number

Question time1）Which of the following is Arithmetic Series ?

A. 1, 2, 4, 8, 16, 32…

B. 1, 3, 5, 7, 9, 11…

C. 5, 7, 2, 4, 1, 8…

D. 113, 123, 513, 274… B

an=a1+(n-1)d

2）Which of the following is Geometric Series ?

A. 6, 5, 8, 123, 213…

B. 5, 10, 15, 20, 25, 30…

C. 3, 9, 27, 81, 243…

D. 7, 11, 7654, 1239123… c

an=a1rn-1

Thank YouThank You