Precalculus (6th Edition) Blitzer

First three terms are: $8,13,18$; Last term =88 and Sum is 816
Formula to calculate the nth term of an arithmetic sequence is: $a_n=a_1+d(n-1)$ Here, $a_1:$ First term and $d=$ common difference Need to find the first three terms. $a_1=8+5(1-1)=8;\\a_2=8+5(2-1)=13;\\a_3=8+5(3-1)=18$ Now,$a_{17}=8+5(17-1)=88$ Formula to calculate the sum of an arithmetic sequence is: $S_n=\dfrac{n}{2}(a_1+a_n)$ Thus, $S_{17}=\dfrac{17}{2}(8+88)=816$ Hence, First three terms are: $8,13,18$; Last term =88 and Sum is 816