Q: derivative of some function I have the following function :
$$f_{x}\left(x,s\left(x,z\left(x\right)\right)\right)$$
When I try to differentiate it according to $x$, I find something but I am not sure :
$$f_{xx}+f_{xs}s_{x}+f_{xs}z_{x}\left(x\right)$$
Am I right ?

A: No, it should be
$$f_{xx}+f_{xs}s_{x}+f_{xs}s_zz_{x}\left(x\right)$$
Since $s$ is a function of $(x,z)$
