Positive term series is positive term series,

A negative column is a negative column, (the reverse sequence of a positive sequence)

The partial sum sequence {Sn} of a positive sequence is monotonically increasing,

There are two possibilities for monotonically increasing sequences:

(1) bounded, there is a limit,

At this time, the corresponding positive series converges;

(2) boundless, then due to monotonous increase,

It tends to-∞.

At this point, the positive series diverges to-∞.

The negative series has a similar conclusion.