. Do the following series converge absolutely or diverge? Write one sentence to explain your answer, and specify which test you used (3 marks each]. \text { (a) } \sum_{n=0}^{\infty} \frac{(-1)^{n} n^{2 n}}{2^{n}\left(n^{2}+1\right)^{n}} \text { (b) } \sum_{n=0}^{\infty} \frac{(2 n+1) !}{n !(n+1) !}

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