Can Leibniz's criterion for alternating series be used to show divergence?
If the test fails, can you conclude that the given series diverges?
Can Leibniz's criterion for alternating series be used to show divergence?
If the test fails, can you conclude that the given series diverges?
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One of the hypotheses of the Leibniz criterion is that the $n$-term of the series goes to zero. If this condition is not satisfied then indeed the series is divergent.
The other condition is that the absolute value of the $n$-th term is a monotone function of $n$. The failure of this condition does not necessarily imply that the series is divergent.