Estimate the area under the graph of f(x)=1+x^2 from the points x=-1 and x=2 using three rectangles. THEN improve your estimate by using six rectangles. What can you conclude about the area under the curve as the number of rectangles increase?

im not sure how to do this... i know it inovles intergals and maybe Riemann summation? I am not sure...

Thank You So Much!