Answer
$k=-2$ or $k=3$
Work Step by Step
We know that two vectors are orthogonal if their dot product is $0$.
Hence: $u\cdot v=1\cdot k^2-1\cdot k+2\cdot(-3)=0\\k^2-k-6=0\\(k+2)(k-3)=0$
Thus: $k=-2$ or $k=3$
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.