Chapter 11 - Further Topics in Algebra - 11.2 Arithmetic Sequences and Series - 11.2 Exercises - Page 1024: 28

$a_n=53-3n$ $a_8=29$

$a_{15}=8, a_{16}=5$ Determine $d$: $d=a_{16}-a_{15}=5-8=-3$ $a_n=a_1+(n-1)d$ $a_{15}=a_1+(15-1)*d$ $8=a_1+14*(-3)$ $8=a_1-42$ $a_1=50$ $a_n=a_1+(n-1)d$ $a_n=50+(n-1)*(-3)$ $a_n=50-3n+3$ $\boxed{a_n=53-3n}$ $a_8=53-3*8$ $a_8=53-24$ $\boxed{a_8=29}$