I'm having trouble understanding how to get these from these types of problems.

What should I be looking for and how. Any hints, tips , or methods?

Some examples of course would be

1. e^sqrt(z - x^2 - y^2)

2. ln(25 - x^2 - y^2 - z^2)

3. sqrt( 1 + x - y^2)

More than just answering these problems i'm more interested in knowing how to derive the domains and ranges since i'm really gonna need to know it. Thanks in advance guys (Worried)