Differentiation is the rate of change of the value of the function with respect to any change in the value of the independent variable. So, it is of importance to understand what type of function is in a question. Depending upon the function, the treatment of the question changes. Primarily, there are two types of functions:Linear Functions - The rate of change throughout the domain of a linear function is constant. So the rate of change of function is equal to the rate of change at any instant or a given point.Non-Linear Functions - The rate of change varies throughout the domain of the function. So the rate of function is derived at a particular point or an instant.