Let ​ Use a Riemann Sum with Four Subintervals of Equal Length

Let ​
Use a Riemann sum with four subintervals of equal length to approximate the area of R (under the graph of f on the interval [0, 2]). Choose the representative points to be the left end points of the subintervals.
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__________ sq units
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Repeat previous part with eight subintervals of equal length .
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__________ sq units
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Compare the approximations obtained in previous parts with the exact area (12 sq units). Do the approximations improve with larger n?