1) (-1)^n * n^3/3^n Test for abs. convirg.
So they use the ratio test:
| (-1)^n+1 (n+1)^3| | 3^n |
|------------------------| * |-----------------| So you divide or reverse multiply
| 3^n+1 | | (-1)^n n^3 |
Then they get
1
-- ( n+1 / n )^3
3
alright...3^n cancel's w/3^n+1, it's just like having 3*3*3*3*3/3*3*3*3*3*3, you have one more three on the bottom, so all the top 3's go away and just leaves the bottom 3
and what you have left is (n+1)^3 on the top and n^3 on the bottom, all they did is put the ^3 sign outside the paranthasees
whew, i HOPE the questions are going to be this easy on Thursday :Q