Let the series
$\sum_{n=0}^\infty{\frac{a_n}{3^n}}$ be convergent, but the series
$\sum_{n=0}^\infty{\frac{{(-1)^n}{a_n}}{3^n}} $ be divergent.
Show whether:
a)$\sum_{n=0}^\infty{\frac{a_n}{3^n}}$ is absolutely convergent or conditionally convergent
b)$\sum_{n=0}^\infty{\frac{a_n}{2^n}}$ is absolutely/conditionally convergent or divergent
c)$\sum_{n=0}^\infty{\frac{a_n}{4^n}}$ is absolutely/conditionally convergent or divergent
d)Find the convergence radius of $\sum_{n=0}^\infty{\frac{n+2}{n+3}a_nx^n}$
Okay, so far I have solved a), which I found quite easy to do, but I seem to get something wrong at b/c/d could someone please explain how they should be solved as it seems I have blocked completely...