Let y = f(x) be a differentiable function. Check all of the statements that must be true about the differential dy. Ody= Ay dy=df dy is a function involving two independent variables, and dz dy = f'(x) dr Ody is the change in y corresponding to a change Az in z The symbol Ay represents O the derivative of y the change in y O the change in a O the product of A and y The symbol Ax represents O the change in a O the derivative of a O the change in y O the product of A and a O the difference quotient