



 
Hi Sheila, If f(x) = x^{1/3} then you need to evaluate and the numerator is
Let a = (x + h)^{1/3} and b = x^{1/3} and recall the difference of cubes
Multiply the numerator and denominator inside the limit by (a^{2} + ab + b^{2}) and the numerator becomes
and the denominator becomes
The numerator and denominator each have a factor of h which will cancel and then you can take the limit as h approaches zero. I hope this helps,  


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