$\"\"$

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The function is $\"\"$ .

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The subintervals are $\"\"$ .

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Observe the graph:

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The area is bounded between $\"\"$ and $\"\"$ .

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The function is decreasing on interval $\"\"$ .

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Width $\"\"$ .

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The minimum value on each sub interval occurs at the left end point.

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The left end point is $\"\"$ .

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Lower sum is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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The upper sum $\"\"$ square units.

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$\"\"$

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The sum of areas of the circumscribed rectangles is called upper sum.

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The right end point is $\"\"$ .

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The sum of areas of the circumscribed rectangles is called upper sum.

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Upper sum is $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ $\"\"$

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$\"\"$ .

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The Upper sum $\"\"$ square units.

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$\"\"$

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$\"\"$ square units.

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$\"\"$ square units.