1. The problem statement, all variables and given/known data The only thing given is f(z)=x. However, I am under the assumption that z is a complex variable where z=x+iy. I'm also assuming that x is a real variable. In this example, I know that f(z)=x is not differentiable with respect to z because it does not satisfy the Cauchy-Riemann Equations but I need to prove this using the limit definition of the derivative. 2. Relevant equations I used the definition of the limit i.e. limit as h→0 [f(x+h)-f(x)]/h however I'm not quite sure what f(x+h) translates into in this problem. 3. The attempt at a solution this may be a straight forward question that I'm over thinking but I get lim Δz→0 [Δx/Δz] which does not exist. Is that correct? This is my first post. I don't know how to enter math notation that is easier to read. Help with that would also be appreciated.