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