Question 1190590
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            Actually,  you ask us,  the tutors,  re-write again specially for you what is written in tens  Calculus textbooks.


            Every  Calculus student must have and read at least one such source.


                    If you do not understand what is written there,  then you deserve a special reward . . . 


            If you do not have such a textbook on your table,  you may learn the subject from the Internet.



To learn on " HOW TO differentiate from first principles ",   read from these  Internet sources



https://www.siyavula.com/read/maths/grade-12/differential-calculus/06-differential-calculus-02


https://owlcation.com/stem/How-to-Differentiate-from-First-Principles



You will find full explanations there.