The concept of " function" is corner stone of mathematics. Those who had basic idea of " function" can be well versed and will be able to understand concept of calculus: LIMITS, CONTINUITY, DIFFERENTIABLITY.
please give suggestions how to dovelop this idea
Development may be
1)Giving examples: Area of circle is function of radius , and establishing there is a relation between two variables and establishing how one quantity will depend on another quantity
2)Giving idea of taking equation:
a)making table of values:
b)ploting equation graphically
3)Function as a relation
4)Establishing a fact that a line parallel to y axis cuts the graph of a function at one point.
4)Giving examples of expression which is not a function
5) with conclusion etc etc
please suggest the steps to be involved systematically