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To simplify this expression you can first expand (x + h)^{3} using the binomial theorem but I think it's easier to regroup
and then factor (x + h)^{3}  x^{3} as a difference of cubes. Once you have done this and simplified the expression [(x + h)^{3}  x^{3}] + h you will see that there is a common factor of h. Thus when you form the difference quotient by dividing by h, as long as h is not zero you can cancel the denominator with the common factor of h in the numerator. Try this and if you have difficulties write back. Harley
Sue, The difference of cubes expression is
In your expression a = x + h and b = x so you get
Can you finish it now? Harley  


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