Total and Partial Derivative

Hello. I have seen the below in a book

(1)

How to derive the above (1)?

I know the below (2) for the relation between total & partial derivative.

(2)

I substitue & expand, but there are few terms that I cannot cancel out & I don't see any minus term that appear in (1)

Are there anything that I have missed? How to derive (1)?

Thank you.