Estimate the Area Under the Graph Of $f ( x ) = x ^ { 2 } - 1$

Essay

Estimate the area under the graph of $f ( x ) = x ^ { 2 } - 1$ from $x = 1$ to $x = 5$ using
(a) four approximating rectangles and right endpoints.
(b) four approximating rectangles and left endpoints.
(c) eight approximating rectangles and right endpoints.