Examine the series _ n=1 ^ (-1)^ n 3n^ 2 +5 4n^ 3 -n

MATHEMATICS · Single correct · AP · Calculus BC · Infinite Sequences and Series · Infinite Sequences and Series

Problem

Examine the series ∑n=1∞(−1)n3n2+54n3−n.\sum_{n=1}^{\infty}(-1)^{n}\frac{3n^{2}+5}{4n^{3}-n}. Which of the following correctly describes its convergence? (a) It diverges because its terms do not tend to 00 (the limit is 34\tfrac34). (b) It converges conditionally but not absolutely. (c) It converges absolutely by the Ratio Test since lim⁡n→∞∣an+1an∣=34<1\displaystyle\lim_{n\to\infty}\left|\frac{a_{n+1}}{a_n}\right|=\tfrac34<1. (d) It converges absolutely because the series of absolute values is a pp-series with p>1p>1.

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