Answer
$61$
Work Step by Step
$\sum\limits_{k=1}^6(k^2-5)=\sum\limits_{k=1}^6k^2-\sum\limits_{k=1}^65-=(1^2+2^2+3^2+4^2+5^2+6^2)-6\cdot5=(1+4+9+16+25+36)-30=91-30=61$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.