Originally Posted by

**aquaglass88** Hi I am trying to find use the definition of the definite integral to prove that

the integral of (x^2)dx in [a,b] = [(b^3) - (a^3)]/3

I started out using the Reiman Sums except I ended up with

lim as n approaches infinity [nab^2 - bab^2 + b^3 - na^3 + a^3 - ab^2]^2

-------------------------------------------------------

n^2

I have no clue how that equals b cubed minus a cubed over 3 and I'm not sure what I did wrong if I did.

THanks so much for your help!!