Question 1203098
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        Derivative by first principle refers to using algebra and limits
        to find a general expression for the slope of a curve. 
        It is also known as the delta method.



What Edwin used in his solution,  is  NOT  first principle method.


Taking derivative with the use of table functions  IS  NOT  first principle.


See your  Calculus textbook and/or many sources in the  Internet,  like these


https://www.google.com/search?q=what+is+first+principle+taking+derivative&rlz=1C1CHBF_enUS910US910&oq=what+is+first+principle+taking+derivative&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigAdIBDjU3NDQzMTg3NWowajE1qAIAsAIA&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:c5156776,vid:2WbxMN6Y0hk,st:15


https://www.youtube.com/watch?v=KdakN2VJIMY


https://www.youtube.com/watch?v=gxwbNdBlEMw


https://en.wikipedia.org/wiki/Derivative