- #1

thoradicus

- 45

- 0

## Homework Statement

Hey all, been having some problem with the rule..technique looks right but doesn't agree with wolfram's calc answer. Doing a moment generating function problem.

M(t)=(e^5t-e^4t)/t, Find EX and VARX

## Homework Equations

M'(0)=e(x) and so on..

## The Attempt at a Solution

Okay, this is an indeterminate equation.. thats why I had to use this rule.. But my answer keeps getting 9 while wolfram says 9/2, so I need some help here.

Ok, using quotient rule, differentiating, I get (5e^5t-4e^4t)/t + (e^4t-e^5t)/t^2. Correct me if Im wrong.

I separated the latter part of the equation into ((e^4t-e^5t)/t)(1/t), which then equals to (-1)(1/t)

Therefore, I get (5e^5t-4e^4t-1)/t, which is indeterminate again, differentiating both nominators, i get 9. What have I done wrong?