### Home > CCG > Chapter 4 > Lesson 4.1.5 > Problem4-51

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 $a_n$.

Refer to the Math Notes box in Lesson 4.1.3.

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

1. $\frac { 1 } { 2 }$, $\frac { 1 } { 4 }$, $\frac { 1 } { 8 }$, $\dots$

$r=\frac{1}{2}$

1. $-7.5$, $-9.5$, $-11.5$$\dots$

One equation for an arithmetic sequence is:
$a_n=m(n-1)+a_1$

Arithmetic;
$a_n=-2(n-1)-7.5=−2n-5.5$