Answer
$|x+6|$
Work Step by Step
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$.
$\sqrt[n] {a^n}=|a|$ if $n$ is even.
Hence here: $\sqrt{x^2+12x+36}=\sqrt{(x+6)^2}=|x+6|$
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.