September 12, 2017September 18, 2017 my arithmatic sequence PART1: 1,3,5,7,9……. t50=t1+(n-1)d t50=1+49*2=99 tn=1+(n-1)*2=1+2n-2=-1+2n PART2: Sn=n/2(t1+t50)=25*(1+99)=2500