What is the formal proof that a sequence diverges

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The discussion focuses on proving the divergence of the sequence defined by the expression (n^2 + 1)/n as n approaches infinity. The limit of this sequence is confirmed to be infinity, establishing that it diverges. A formal proof involves demonstrating that for any large positive number M, there exists a number N such that for all n ≥ N, the sequence terms a_n exceed M. This is achieved by solving the inequality (n^2 + 1)/n > M to find an appropriate N.

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transgalactic
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i got (n^2+1)/n
when n->infinity the limit is infinity.
what is the formal proof that a sequence diverges ?
 
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I don't know the formal proof off by heart, but you could use L'Hopital's rule to see that it diverges(?).
 
transgalactic said:
i got (n^2+1)/n
when n->infinity the limit is infinity.
what is the formal proof that a sequence diverges ?

Show that for any (large, positive) number M, there exists another number N for which, if n >= N, then a_n > M.

So someone gives you a number M.
You find another number N so that a_N+1, a_N+2, a_N+3, ... all are larger than M.

For your sequence, solve (n^2 + 1)/n > M for n. From that, choose a number N.

Clear?
 

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