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Question
Find the derivative of f(x) = `1/x` by first principle.
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Solution
By definition,
f'(x) = `lim_(h -> 0) (f(x + h) - f(x))/h`
= `lim_(h -> 0) 1/h 1/(x + h) - 1/x`
= `lim_(h -> 0) (-h)/(h(x + h)x)`
= `(-1)/x^2`.
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