I am only starting learning calculus and it's difficult for me to understand the main concept behind calculus ideas particularly differentiation I have searched many resources but most of them are very similar explaining things with words like "speed", "rate of change", "tangent" and "function change in respect to input change"... I know the rules of computation but the purpose is not very clear for me
I would be very grateful if somebody could help me grasp this concept and explain why one would want to compute the "rate of change" of a function and what exactly problem do derivatives solve.
Pretend that I am very stupid (unfortunately I am :) ) and don't use any abstract concepts (even if they are intuitive to a human being ) as "speed" if possible Thanks