# Thread: e related limit

1. ## e related limit

[Math]
\displaystyle \lim_{x \to + \infty} \left( 1 + \frac {3}{x} \right)^{x/2} =
[/tex]

I am simply stumped with this problem.
All I can say, is there is almost an e in there.

$\displaystyle (1+\frac{1}{x})^{x}$
This needs to be somehow factored out correct?

Can someone please guide me through this?
Much appreciated.

2. Originally Posted by Vamz
[Math]
\displaystyle \lim_{x \to + \infty} \left( 1 + \frac {3}{x} \right)^{x/2} =
[/tex]

I am simply stumped with this problem.
All I can say, is there is almost an e in there.

$\displaystyle (1+\frac{1}{x})^{x}$
This needs to be somehow factored out correct?

Can someone please guide me through this?
Much appreciated.
let ...

$\displaystyle \displaystyle t = \frac{x}{2}$

$\displaystyle x = 2t$

[Math]
\displaystyle \lim_{t \to + \infty} \left( 1 + \frac {3}{2t} \right)^{t} = e^{\frac{3}{2}}
[/tex]

3. Thanks. But I still don't really understand how you got there.
I think I understand why you set t=x/2, but after that, you've lost me.

Could you please include the in-between steps?
Thanks!

skeeter just did a change of variable, and $\displaystyle \displaystyle \lim_{n \to \infty} \left( 1 + \frac xn \right)^n = e^x$