I may just be really tired, but can you explain in more detail how "to apply it correctly"? I've tried plugging in the substitutions for x,y,z, since before I even posted on this forum, and I don't understand what I'm doing wrong.
I've been working on this one for a little bit, and I know I really just need to use the chain rule to solve it, but I can't seem to figure out how to set it up properly. Probably a dumb question, but I could really use some help on this!