please help thank you
Shane on an extension of yours, how would i incorporate that in to the comparison test though or some other series test?
Assuming that the sum starts at n = 1, break the sum up into
sum(n=1 to infinity)(n/n^2) - sum(n=1 to infinity)(1/n^2) =
sum(n=1 to infinity)(1/n) - sum(n=1 to infinity)(1/n^2).
Now the second of these sums converges to ((pi)^2 / 6), but the first
of the sums is the harmonic series, which is known to diverge.
Edit: A more formal approach would be to use the limit comparison test with
the harmonic series sum(1/n), where we find that
lim(n->infinity)[((n-1)/n^2) / (1/n)] =
lim(n->infinity)((n-1)/n) = lim(n->infinity)(1 - (1/n)) = 1.
Since this value is finite the limit comparison test tells us that the two
series either both converge or diverge. Since the harmonic series diverges,
we can thus conclude that the given series also diverges.
for n>1 it is strictly non-negative. Hence if it converges, it converges absolutely and can be rearranged and/or the sum can be broken up.
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Assuming that the sum starts at n = 1, break the sum up into
sum(n=1 to infinity)(n/n^2) - sum(n=1 to infinity)(1/n^2) =
sum(n=1 to infinity)(1/n) - sum(n=1 to infinity)(1/n^2).
Now the second of these sums converges to ((pi)^2 / 6), but the first
of the sums is the harmonic series, which is known to diverge.
Edit: A more formal approach would be to use the limit comparison test with
the harmonic series sum(1/n), where we find that
lim(n->infinity)[((n-1)/n^2) / (1/n)] =
lim(n->infinity)((n-1)/n) = lim(n->infinity)(1 - (1/n)) = 1.
Since this value is finite the limit comparison test tells us that the two
series either both converge or diverge. Since the harmonic series diverges,
we can thus conclude that the given series also diverges.
for n>1 it is strictly non-negative. Hence if it converges, it converges absolutely and can be rearranged and/or the sum can be broken up.