"let f be a differentiable function of three variables, and define w(x,y,z) = f(x-y,y-z,z-x). use the chain rule to show dw/dx + dw/dy + dw/dz = 0". i am confused by this question because, in what i am meant to show, there is no f, i.e. it all comes from the w. so i don't know what part of what i am supposed to differentiate to show this. i also don't know what version of the chain rule i am meant to use. since i have notes on the chain rule that pertain to something entirely different. can someone help? thank you