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stunner5000pt
Mar2-04, 10:14 PM
i'm stuck trying to prove this little inequality:

(1+ 1/n)^n <= e <= (1+1/n)^n+1
is there a way to prove this without without resorting to power series for e (because we're not allowed to, and we don't know this yet) and also note that n is a natural number, (positive integer).

cookiemonster
Mar2-04, 10:47 PM
Here's a hint:

\lim_{n \to \infty} \Big( 1 + \frac{1}{n} \Big)^n = e

cookiemonster

stunner5000pt
Mar2-04, 10:59 PM
ok i know tha already i just dont know how to prove it give me hint on hwo to prove it

cookiemonster
Mar2-04, 11:39 PM
Just how formally do you want to prove it?

It's pretty easy to notice that for n<\infty, the left side is less than e. When n = \infty, it is exactly equal to e.

The same holds true for the right side, except that it's always greater than e except when n = \infty.

cookiemonster

matt grime
Mar3-04, 04:53 AM
You do it by power series for (1+x)^n valid when |x|<1 (ie x=1/n)

Wooh
Mar3-04, 07:48 PM
Originally posted by stunner5000pt
i'm stuck trying to prove this little inequality:

(1+ 1/n)^n <= e <= (1+1/n)^n+1
is there a way to prove this without without resorting to power series for e (because we're not allowed to, and we don't know this yet) and also note that n is a natural number, (positive integer).
Why can you not just reason that (1+1/n)^n has to be less than (1+1/n)^n * (1+1/n), as, until n => infinity, 1+1/n will always be a positive value above * a positive value that will always make the right hand larger.