Question

Interval of Convergence question attached

Answer 1

You need to use the Ratio Test which is \[\lim_{k \rightarrow \infty} \left| \frac{a _{n+1}}{an} \right|\] where its convergent when the ratio is < 1

Answer 2

but how wud i do taht using k's?

Answer 3

Ok since we're taking the absolute value the (-1)^k goes away.