1. The problem statement, all variables and given/known data Consider the PDE: [tex]2dz/dx[/tex] - [tex]dz/dy[/tex] = 0 How can I show that if f(u) is differentiable function of one variable, then the PDE above is satisfied by z = f(x +2y)? Also, the change in variables t = x+2y, s=x reduces the above PDE to [tex]dz/dt[/tex] = 0. But how can I show this? 3. The attempt at a solution I simply don't understand, these are my notes from class today and I want to understand while it's early... All I know is that this involves the chain rule.