Open Question: How to use Riemann sums for this expression?

Let f(x)= 2 + x^3 , 1 less then or equal to x less than or equal to 4. Use the idea of Riemann sums to find an expression for the area under the graph of f as a limit. You do not need to evaluate the limit.

Find the 3rd and 6th approximations of the sum in part a.

Please help. I cannot figure this out.

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