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Find the derivative of f(x) = x3, by first principle. - Mathematics

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Question

Find the derivative of f(x) = x3, by first principle.

Sum

Solution

By definition,

f'(x) = `lim_(h -> 0) (f(x + h) - f(x))/h`

= `lim_(h -> 0) ((x + h)^3 - x^3)/h`

= `lim_(h -> 0) (x^3 + h^3 + 3xh(x + h) - x^3)/h`

= `lim_(h -> 0) (h^2 + 3x(x + h))`

= `3x^2`

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Chapter 13: Limits and Derivatives - Solved Examples [Page 230]

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NCERT Exemplar Mathematics [English] Class 11
Chapter 13 Limits and Derivatives
Solved Examples | Q 8 | Page 230

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