### Home > CCA > Chapter 7 > Lesson 7.1.1 > Problem7-15

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.

1. $108,120,132,\dots$

$a_{1} = 108a$
$a_{n+1} = a_{n}+12$

1. $\frac { 2 } { 5 }$,$\frac { 4 } { 5 }$,$\frac { 8 } { 5 }$, …

$a_1=\frac{2}{5}$

$a_{(n+1)} = 2a_{n}$

1. $3741,3702,3663,\dots$

Is the sequence arithmetic or geometric?

1. $117,23.4,4.68,\dots$

Is the sequence arithmetic or geometric?