9. Let {an} be a sequence such that a0 = 1 and

(n2 +2)an+1 – (n2 + 1)pan = 0 for n >= 0.

 

What are all the values of p for which the series

is absolutely convergent?

 

A. {p | p > 1}

B. {p | p < -1}

C. {p | |p| < 1}

D. {p | |p| < 2}

E. {p | |p| < 1/2}

 

Solution: The answer is C

 

Since,

By the ratio test, if

Then,

 

 

is absolutely convergent for |p| < 1. Since,

Then,

is absolutely convergent for all values of p such that –1 < p < 1.