Question 1117124
The common difference is 9-4=5. 4 is {{{a[1]}}} and 9 is {{{a[2]}}} so we need to figure out what is {{{a[25]}}}. 25-1=24  {{{4+24(5)=a[25]}}}

{{{highlight(a[25]=124)}}} For a. Now for b. The formula for finding the first n terms of an arithmetic sequence is {{{n*((a[1]+a[n])/2)}}}.The 60th term is {{{4+59(3)=a[60]}}}

{{{4+177=a[60]}}} {{{highlight(a[60]=181)}}} Plug in the numbers,

{{{60*((4+181)/2)=a[1]+a[2]+a[3]+...}}}{{{+a[58]+a[59]+a[60]}}}

{{{highlight(60*(185/2)=5550)}}}