Answer
$3+4+...+(n+2)$
Work Step by Step
$\sum_{k=1}^{n} (k+2)=(1+2)+(2+2)+...+(n+2)=3+4+...+(n+2)$
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.