A cargo train leaves Chicago at noon travelling west at 120 km/h. At 2 pm, a passenger train leaves Chicago travelling east at 3
2 answers:
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An alternating series 
converges if 
is monotonic and 
as 
. Here 
.
Let
. Then 
, which is positive for all 
, so 
is monotonically increasing for . This would mean 
must be a monotonically decreasing sequence over the same interval, and so must 
.
Because is monotonically increasing, but will still always be positive, it follows that as .
So, converges.
Let
Because
So,