Limit Definition of a Derivative

(Original question is written in long answer. Multiple choice has been used here for convenience)

Let f(x)=xx3\displaystyle f(x) = \frac{x}{x - 3}. Compute dfdx\displaystyle \frac{df}{dx} using the definition of the derivative. No marks will be given for the use of derivative rules, but you may use them to check your answer.

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