Math: Calculus
posted by REALLY NEED HELP!!!! .
Estimate the area under the graph of
f(x)=3x^3+5
from x=1 to x=4, first using 5 approximating rectangles and right endpoints, and then improving your estimate using 10 approximating rectangles and right endpoints.
I'm having problem with using the midpoint to find the area. With 5 rectangle I have 210.625 but I can't figure out how to do the 10 rectangle.

again, you cannot estimate to six significant digits.
on the five rectangle, right endpoints, use 4,3,2,1,0 as right endpoints, width 1
area= f(4)*1 + f(3)*1 + ...
now for ten, use 4, 3.5, 3, 2.5....to .5, then area width is .5