$\"\"$

\

The function is $\"\"$ .

\

The subintervals are $\"\"$ .

\

Observe the graph: The area is bounded between $\"\"$ and $\"\"$ .

\

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

\

Width $\"\"$ .

\

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

\

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

\

Lower sum is $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

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

\

$\"\"$

\

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

\

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

\

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

\

Upper sum is $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

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

\

$\"\"$

\

$\"\"$ square units.

\

$\"\"$ square units.