The application of derivative comes from the thought of finding the best solution to solve our problems, such as

- Finding mix number of husbandry animals that is sustainable for farmers to harvest for the whole season.
- Find the optimal unit number of production to maximize the profit

Such problems could be formulated by mathematical formula, mainly function with variable/s then using derivative to find the solution.

Now to begin, we will have to learn the definition of maximum / minimum value of a function: