The area between the curves is approximated by slicing it into three rectangles. This is called a [b][url=https://en.wikipedia.org/wiki/Bernhard_Riemann]Riemann[/url] sum[/b].[br]On your paper, calculate the area of the rectangles to show that their sum matches the value of "left Riemann sum".

How could you make a more accurate approximation? Do it, and compare your approximation to the exact area. Is it closer than the Riemann sum with 3 rectangles?