Calculate Rn for f(x)=-[(x^2)/3]+4 on the interval [0,4] and write the answer as a function of n without any summation signs. Also find lim as n-->infinity of Rn.

I never have trouble calculating actual numbers (ie; R4 or L6, etc) but I always have trouble when I'm given a variable. If someone could work this out for me to put in my notes I would really appreciate it!