Ok 2 questions which I can't solve.
1. Given that the summation of U(r) between n and r=1 is 1/2 n^2
(n^2 -1), show that U(n) = 2n^3 - 3n^2 + n. Henc express summation
of r^3 between n and r =1 in terms of n. [the restults for
summation of r^2 and r between n and r=1 may be assumed]
2. Given that the geometric progression, whose 1st 2 terms are a
and b (a,b are non-zero), has a sum to infinity of (a+4b), find the
value of summation of (b/a)^r between r=1 and infinity.
Answer is 3.
Thanks!