CPM Homework Help : CCA2 Problem B-14

For parts (a) and (b), find a recursive equation in $a_n$ form for each sequence. (For a reminder about $a_n$ form see the Math Notes box in Lesson A.3.2.) For parts (c) and (d) find an explicit equation for each sequence.

$108, 120, 132, …$
Hint (a):
What is $a_1$ ? How are the terms changing?
Answer (a):
$a_1 = 108, a_{n+1} = a_n + 12$

$\frac { 2 } { 5 }, \frac { 4 } { 5 }, \frac { 8 } { 5 }, …$
Hint (b):
First find the generator for the sequence.
Answer (b):
$a_1 = \frac{2}{5}, a_{n+1} = 2a_n$

$3741, 3702, 3663, …$
Hint (c):
Is the sequence arithmetic or geometric?

$117, 23.4, 4.68, …$
Hint (d):
Is the sequence arithmetic or geometric?