Hi can someone help to explain why we consider negative values since z is encased in an absolute value symbol? Thank you in advance.

That’s the whole point of the absolute value function - it returns the positive component of a number. So that’s why we can consider a negative (or positive) value, as we’ll get a positive value in the end.

Thanks, actually you are right (certainly right!). It’s about the unit, rather than the positive / negative integer for the final answer.