Results from Algebra II can sometimes be used to evaluate definite integrals. Recall that for each integer m:
1 + 2 + ... + (m − 1) + m = (1/2)(m)(m + 1)
Similar methods go back to Archimedes almost 2000 years before Newton invented calculus!
(i) Let f be the function defined on the interval [0, b] by
f(x) = 3x
and P = {0, b/n, 2b/n, ..., (n-1)b/n, b}
the partition subdividing [0, b] into n subintervals of equal length. Use the fact that
1 + 2 + ... + (m − 1) + m = (1/2)(m)(m + 1)
is true for all integers m to find the value of the Upper Sum Uf (P).