1. ## integration

$\displaystyle \int_0^\infty e^{-\frac{x}{y}} dx$

2. Originally Posted by Pengu

$\displaystyle \int_0^\infty e^{-\frac{x}{y}} dx$
It's an improper integral so the first step is: $\displaystyle \lim_{\alpha \rightarrow + \infty} \int_0^\alpha e^{-\frac{x}{y}} dx$.

If you need more help please show all your working and say where you're stuck.

3. 1. Integral of $\displaystyle e^{-x/y}$ function is $\displaystyle -y*e^{-x/y} + C$.
2. $\displaystyle -y*e^{-x/y} -> 0$ when $\displaystyle x -> +inf$

Then the answer is $\displaystyle y$

4. Originally Posted by ialbrekht
1. Integral of $\displaystyle e^{-x/y}$ function is

$\displaystyle -y*e^{-x/y} + C$.

2. $\displaystyle -y*e^{-x/y} -> 0$ when $\displaystyle x -> +inf$

Then the answer is $\displaystyle y$
Not clear enough (or may-be just wrong) , what happens if y<0?? Also what happens when y>0??

CB

5. i was about to say that but i forgot.

calculations are valid for positive values. (The integrand is a positive function, it's impossible to get a negative number.)