Answer
3i
Work Step by Step
To express in terms of $i$ simply divide the number under the radical by -1 and write i as a multiplier. $\sqrt 9=3$. Thus the answer is 3i.
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.