Chapter 9 - Conic Sections, Sequences, and Series - 9.3 Arithmetic Sequences - 9.3 Exercises - Page 727: 13

$-1,\frac{1}{4},\frac{-1}{9},\frac{1}{16},\frac{-1}{25}$

$a_n=\frac{(-1)^n}{n^2}$ $a_1=\frac{(-1)^1}{1^2}=-1$ $a_2=\frac{(-1)^2}{2^2}=\frac{1}{4}$ $a_3=\frac{(-1)^3}{3^2}=\frac{-1}{9}$ $a_4=\frac{(-1)^4}{4^2}=\frac{1}{16}$ $a_5=\frac{(-1)^5}{5^2}=\frac{-1}{25}$