Solving infinite limit at infinity

1. May 30, 2010

K29

Solving infinite limit at infinity[solved]

Really need help here. I somehow missed a fundamental principle and I have an Analysis exam tomorrow

I need to use this definition for $$lim_{n\rightarrow\infty}a_{n}=-\infty$$:

For all A<0 there exists $$K_{A}>0$$,
$$x>K_{A}$$
such that f(x)<A. I perfectly understand this.

Now i need to use it to show:
$$lim_{n\rightarrow\infty}(3n-2n^{2})=-\infty$$
I can do it for a specific case using the definition, like for n>=2 its clear that f(x) will be less than 0, using the definition. But I am not sure that this is a general proof. I.e. that doesn't show that f(x) will tend to infinity.

[ok I solved it and dont know how to delete the post so ya. shud have checked out "related threads" before posting sorry]

Last edited by a moderator: May 31, 2010