Posted by Tabby on .
Express the series 11 + 18 + 27 +...+ 171 using sigma notation.
Usually you would take 27-18 and that's the step between numbers, right? (I think its the k-value?) But 27-18=9 and 18-11=7. Are we stepping by k+2 here? Like k, k+2 k+4, k+6...?
Please help me. I'm not confident in sigma notation, and this question is difficult for me. Reiny, Damon, and Bobpursley have all given me good feedback before, but any tutor is welcome to respond to this!