Any idea on how to integrate the following?

  • Thread starter Thread starter Amannequin
  • Start date Start date
  • Tags Tags
    Idea Integrate
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
1 reply · 1K views
Amannequin
Messages
4
Reaction score
0

Homework Statement



The c.d.f. of a random variable X is given by the following formula

F(x) = 1 - e-x2 x≥0

Find M(t). Moment generating function.

The Attempt at a Solution



I've found the pdf as

f(x) = F'(x) = 2xe-x2 x≥0

To determine M(t) I need to do the following

M(t) = E(etX) = ∫etx 2xe-x2

Then I'm not sure how to go about integrating. Any ideas or clues to point me in the right direction will be greatly appreciated. Thanks.
 
Physics news on Phys.org
Try completing the square: ##x^2 - tx = x^2 - tx + (t/2)^2 - (t/2)^2 = (x - t/2)^2 - (t/2)^2##, so
$$\int e^{tx}2xe^{-x^2}dx = e^{(t/2)^2} \int 2x e^{-(x-t/2)^2} dx$$
which should be manageable with a bit more work.
 
  • Like
Likes   Reactions: 1 person