Estimate $\int _ { 2 } ^ { 5 } 1 + x ^ { 2 } d x$

Essay

Estimate $\int _ { 2 } ^ { 5 } 1 + x ^ { 2 } d x$ using three approximating rectangles and taking the sample points to be left endpoints. Use a picture to explain why your estimation is an overestimate or an underestimate.