MHB Convergence Condition for Applying Ratio Test to Power Series

alexmahone
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Given a power series, what is the condition on its coefficients that means the ratio test can be applied?
 
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Alexmahone said:
Given a power series, what is the condition on its coefficients that means the ratio test can be applied?

I think it can always be applied. Other test just may be easier for a given power series.
 
Alexmahone said:
Given a power series, what is the condition on its coefficients that means the ratio test can be applied?

You actually should always do the ratio test on the series of ABSOLUTE VALUES, to prove absolute convergence (i.e. to show the series is bounded both above and below by the series of absolute values and the negative of the series of absolute values).
 
A sphere as topological manifold can be defined by gluing together the boundary of two disk. Basically one starts assigning each disk the subspace topology from ##\mathbb R^2## and then taking the quotient topology obtained by gluing their boundaries. Starting from the above definition of 2-sphere as topological manifold, shows that it is homeomorphic to the "embedded" sphere understood as subset of ##\mathbb R^3## in the subspace topology.
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