reading a book about statistical mechanics (kerson huang chapter 3) I got a trouble understanding the following: We have
$f(r+v\delta t, v+ F/m\delta t, t+\delta t)=f(r,v,t)+K\delta t$
and then''expanding the left-hand side to first order in $\delta t$'' we obtain:
$(\frac{\partial}{\partial t} + v\cdot\nabla_r+F/m\cdot\nabla_v)f(r,v,t)=K$
Im totally lost, can someone explain me the expansion procedure in this step? and recommend a good book or chapter on expansion? thank you very much