1. The problem statement, all variables and given/known data Given f(x, y, z) = 3x + 2y + 4z, find its rate of change at (1, 2, 3) on the plane y = 2. 2. Relevant equations 3. The attempt at a solution Since y is constant, I don't know if I have to find ∂f/∂x or ∂f/∂z. It's a homework problem, but I don't know if it was bad written by the teacher. Could you help me please?