# Derivative question

1. May 22, 2010

### gomes.

1. The problem statement, all variables and given/known data
[PLAIN]http://img696.imageshack.us/img696/4462/124234c23c423.jpg [Broken]

3. The attempt at a solution

I did the first part already, by letting
u = ax => dx = du/a, then just substituting in the values.

How do i explain why its negative?

Last edited by a moderator: May 4, 2017
2. May 22, 2010

### hgfalling

Try comparing the value of $e^{-x}$ to the value of $(1+x)^{-1}$. Then prove the relationship you find, maybe with series expansions or some other way.

3. May 22, 2010

### LCKurtz

Hint: Its value doesn't depend on α. Find a nice value of α. to try.

4. May 22, 2010

### gomes.

Im still stuck :(

5. May 22, 2010

### LCKurtz

What nice value of α have you tried?