Problem understanding divergence test

[Kolahal Bhattacharya]

I am going through Boas.Ch-1.on infinite series.
Can anyone help?
1.May we use preliminary divergence test for series with +ve and -ve terms?How?For some situation occurs when we are supposed to make out (-1)^infinity

 

[TheloniousMONK]

I am sorry, but you are going to need to be a little more specific about your problem. Recall from your Calculus courses that there a number of different divergence/convergence tests for infinite series.

 

[Kolahal Bhattacharya]

Re divergence test

It says limit a#n as n tends to infinity when not equal to zero, the series diverges.And as a#n tends to zero as n tends to infinity is inconclusive.I want to know, whether a#n may be negative numbers.

 

[HalfManHalfAmazing]

Infinite series use $$n$$ to denote the number of the term in the series, you cannot of a 'negative' term (that I know of) in a series. I am not even sure what you are asking though.