 # Arithmetic and geometric sequences: Identifying and writing an explicit rule Anonymous
timer Asked: Nov 27th, 2015
account_balance_wallet \$5

### Question Description

The sequences below are either arithmetic or geometric.  For each sequence, determine whether i it is arithmetic or geometric, and write the formula for the nth term an of that sequence

TYPE               nth term formula

-6, -8, -10, ...

27, -9, 3, ...

abotsi55
School: Purdue University   Thank you for the opportunity to help you with your question!

-6,-8,-10 is an arithmetic sequence. The first term is a1=-6. The common difference is d=-2.

The n-th term is a(n) = a1 + (n-1)d. Therefore

a(n) = -6 + (n-1)(-2) = -4 - 2n.

n=1:  a(1) = -4 -2(1) = -6

n=2: a(2) = -4 - 2(2) = -8

-----------------

27,-9,3, ... is a geometric sequence.

The first term is a=27. The common ratio is r = -1/3.

The n-th term is a(n) = 27(-1/3)^(n-1) = -81(-1/3)^n

n=1: a(1) = -81(-1/3) = 27

n=2: a(2) = -81(-1/3)^2 = -9

Please let me know if you need any clarification. I'm always happy to answer your questions.

flag Report DMCA  Review Anonymous
Goes above and beyond expectations ! Brown University

1271 Tutors California Institute of Technology

2131 Tutors Carnegie Mellon University

982 Tutors Columbia University

1256 Tutors Dartmouth University

2113 Tutors Emory University

2279 Tutors Harvard University

599 Tutors Massachusetts Institute of Technology

2319 Tutors New York University

1645 Tutors Notre Dam University

1911 Tutors Oklahoma University

2122 Tutors Pennsylvania State University

932 Tutors Princeton University

1211 Tutors Stanford University

983 Tutors University of California

1282 Tutors Oxford University

123 Tutors Yale University

2325 Tutors