Chapter 11 - Sequences; Induction; the Binomial Theorem - Chapter Review - Review Exercises - Page 859: 21

$a_n=n-10$,

1. Start with a general form $a_n=a_1+(n-1)d$, based on the given conditions, we have: $0=a_1+(10-1)d$ or $0=a_1+9d$ 2. Also $8=a_1+(18-1)d$ or $8=a_1+17d$ 3. Take the difference of the above two equations to get $8d=8$, thus $d=1$ 4. Find $a_1=0-9(1)=-9$ 5. The general form is $a_n=-9+(n-1)=n-10$,