Chapter 11 - 11.2 - Arithmetic Sequences and Partial Sums - 11.2 Exercises - Page 786: 13

$a_1=8$ $a_2=11$ $a_3=14$ $a_4=17$ $a_5=20$ It is an arithmetic sequence. $d=3$

$a_n=5+3n$ $a_1=5+3(1)=5+3=8$ $a_2=5+3(2)=5+6=11$ $a_3=5+3(3)=5+9=14$ $a_4=5+3(4)=5+12=17$ $a_5=5+3(5)=5+15=20$ A sequence is arithmetic if $a_2−a_1=a_3−a_2=a_4−a_3=a_5−a_4=...=d$ For the given sequence we have that: $a_2-a_1=11-8=3$ $a_3-a_2=14-11=3$ $a_4-a_3=17-14=3$ $a_5-a_4=20-17=3$ It is an arithmetic sequence. Common difference: $d=3$