d'Alembert's test for convergence

d'Alembert's test for convergence

[¦dal·əm¦bərz ‚test fər kən′vər·jəns]
(mathematics)
A series ∑ an converges if there is an N such that the absolute value of the ratio an / an-1is always less than some fixed number smaller than 1, provided n is at least N, and diverges if the ratio is always greater than 1. Also known as generalized ratio test.
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