CPM Homework Help : CCG Problem 4-51

Examine each sequence below. State whether it is arithmetic, geometric, or neither. For the sequences that are arithmetic or geometric, find the equation for $t(n)$ or $a_n$ .

Hint:

Refer to the Math Notes box in Lesson 4.1.3.

More Help:

Are the sequences changing at a constant rate by addition or multiplication?

$\frac { 1 } { 2 }$ , $\frac { 1 } { 4 }$ , $\frac { 1 } { 8 }$ , $\dots$
Hint (a):
$r=\frac{1}{2}$

$-7.5$ , $-9.5$ , $-11.5$ , $\dots$
Hint (b):
One equation for an arithmetic sequence is:
$a_n=m(n-1)+a_1$
Answer (b):
Arithmetic;
$a_n=-2(n-1)-7.5=−2n-5.5$