list the first 5 partial sums of the series...?

Question

list the first 5 partial sums of the series: from 1 to infinity of 5*(-1)^n *n^3

Answer 1

First, find the first five terms:
5(-1)(1^3) = -5
5(-1)^2 (2^3) = 40
5(-1)^3 (3^3) = -135
5(-1)^4 (4^3) = 320
5(-1)^5 (5^3) = -625

So the first five partial sums are:
-5, 35, -100, 220, -405
where you just take each partial sum and add the next term in the sequence.