CPM Homework Help : CCA Problem 7-15

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 5.3.2.) For parts (c) and (d) find an explicit equation for each sequence.

$108,120,132,\dots$
Answer (a):
$a_{1} = 108a$
$a_{n+1} = a_{n}+12$

$\frac { 2 } { 5 }$ , $\frac { 4 } { 5 }$ , $\frac { 8 } { 5 }$ , …
Answer (b):
$a_1=\frac{2}{5}$
$a_{(n+1)} = 2a_{n}$

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

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