`sum_(n=1)^oo (-1)^(n+1)/(nsqrt(n))` Determine whether the series converges absolutely or conditionally, or diverges.
To determine the convergence or divergence of the series `sum_(n=1)^oo (-1)^(n+1)/(nsqrt(n))` , we may apply Alternating Series Test . In Alternating Series Test, the series `sum (-1)^(n+1) a_n ` is convergent if: 1) `a_ngt=0` 2) ` a_n` is monotone and decreasing sequence. 3) `lim_(n-gtoo) a_n =0` For the series `sum_(n=1)^oo (-1)^(n+1)/(nsqrt(n))` , we have: `a_n = 1/(nsqrt(n))` Apply the radical property: `sqrt(x) =x^(1/2)` and Law of Exponents: `x^n*x^m =x^(n+m).` `a_n = 1/(nsqrt(n))` `=1/(n*n^(1/2))` `=1/n^(1+1/2)` `=1/n^(3/2)` The `a_n =1/n^(3/2) ` is a decreasing sequence. Then, we set-up the limit as : `lim_(n-gtoo)1/n^(3/2) = 1/oo =0` By alternating series test criteria, the series `sum_(n=1)^oo (-1)^(n+1)/(nsqrt(n))` converges . The series `sum_(n=1)^oo (-1)^(n+1)/(nsqrt(n))` has positive and negative elements . Thus, we must verify if the series converges absolutely or conditionally. Recall: a) Absolute Convergence : `sum a_n` is absolutely convergent if `...