Question 552673
Recall that the square root of a quantity always gives two answers, a positive answer and a negative answer.
If you want to indicate that only yhe positive answer applies, then you would us the absolute value sign.
Example, to indicate that only the positive answer applies:
{{{sqrt(x^2) = abs(x)}}}
In your problem:
{{{sqrt(z^2+8z+16) = sqrt((z+4)^2)}}}={{{abs(z+4)}}}