Answer
$-|x-4|$
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: $-\sqrt{x^2-8x+16}=-\sqrt{(x-4)^2}=-|x-4|$
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.