Use rectangles to find the estimate of each type for the area under the given graph of $f$ from $x=0$ to $x=8.$

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1. Use four rectangles and take the sample points from the left-endpoints.
Answer: $L_4 =$

2. Use four rectangles and take the sample points from the right-endpoints.
Answer: $R_4 =$

3. Use eight rectangles and take the sample points from the left-endpoints.
Answer: $L_8 =$

4. Use eight rectangles and take the sample points from the right-endpoints.
Answer: $R_8 =$

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Note: You can click on the graph to enlarge the image.

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