Help with a thermo derivation?

Hi all, first post so I hope this is ok to go here. It's not a homework question, just something in my book I don't get...

I am looking through my thermodynamics textbook (Smith,Van Ness, and Abbot, Intro to Chemical Eng thermodynamics) and they give the eq (6.19):

([tex]\partial[/tex]H/[tex]\partial[/tex]P)T = V - T([tex]\partial[/tex]V/[tex]\partial[/tex]T)P

then, "because V = ZRT/P we can write more concisely:

([tex]\partial[/tex]H/[tex]\partial[/tex]P)T = -RT2/P (([tex]\partial[/tex]Z/[tex]\partial[/tex]T)P)

Can anyone explain to me how they did that? I'm sure there is just some simple substitution I am missing
Nevermind, I went about it by dH/dP = d(U+PV)/dP and it worked out. If an admin can delete this, that would be great.

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving