- #1
Grunting7
- 2
- 0
Homework Statement
∞
n=3 ∑ ((-1)n (x+3)3n)/(2nlnn)
Find radius of convergence, interval of convergence, values for x which series is: absolutely convergent, conditionally converge or divergence.
Homework Equations
The Attempt at a Solution
I applied the Ratio Test and got
|(x+3)3| lim n--> ∞ (-1(lnn))/(ln(n+1))
Then I used l'Hospitals to get the limit and got -1/2.
So then it's -1/2 * |(x+3)3| = L. Then do the radius and interval stuff.
The problem is that it's -1/2 and the radius can't be negative. I've had one or two similar problems where I keep getting a negative radius. Not sure what I am missing.