What is the integral of xe^(-x) dx?

Sorry, my fingers and toes only go to 20.

let me get my maths folder out, two seconds

I think it would just be…. xe^(-x) + c

not sure, but the integral of e to the x equals the function of u sub n. (write it down)

Right when I think I am pretty smart, I see a question like this, and get knocked down a couple of notches, make that a couple, couple notches.
Looks like a foreign language to me!

i found it out its -xe^(-x)(x+1)+c

True. No, Fasle. Yeah, false. Wait… what? Definitely true. I think.

@sarah: It is a foreign language (Calculus); you’d learn it just like you’d tackle French 1, slowly, methodically, and daily.

@gail, not me….I’ll stick with French, french wasn’t anything like that, it was fun to learn!

Algebra & statistic was hard enough, I’ll leave the calculus to you and the rest of the brains here….I have math phobia bad!

@sarah; this question is like starting your first day of French by having to learn the subjunction of *pouvoir.” When you start at the beginning with pre-calculus, it is fun and clear and becomes magical, in its own weird way.

@gail…pre-calculus????????? I barely made it through pre-algebra!

I don’t want to learn it…I have been traumatized enough from math! lol :)

Okay, I will cancel your registration.

@gail lol, I needed that laugh, after seeing that other horrid thing that was posted earlier. Thanks for the laugh! hahaha

(Erk! I meant the “subjunctive”.)

@waterskier2007: You’re right. I just pulled out my old calc 2 book and that example was in one of the chapters.

Saranapnsc, maybe you should focus on English. “Algebra and Statistics were hard enough…”

;-)

@waterskier2007: Now take the derivative of what you got with respect to x and see if that works out for you. :^>

What you want to look for is “integration by parts”.

yeah i did take the derivative just to check. thanks

Then you need to recheck your work because you’re a bit off. Cheers!

no, im not a bit off. i just did it and it works. and i got the right answer using it

Nope. You have an extra x in your answer. If you want to work it through I’ll tell you where you’re going wrong.

ah yeah for sure the extra x at the beginning. my bad indeed

No problem. Are you just learning about integration by parts? I’m just wondering why you asked this question in particular.

no im in calc 4: diff eq but couldnt remember how to do that

Anytime I have an integral I don’t feel like actually doing, I go to Wolfram.

(By the way, TimothyKinney actually just typed that. I showed him the problem, and he is such a geek that he could not resist writing something). Feel free to give me his lurve though ;-) !! The way I see it, he donated it to me when he answered a question on my account.

Ha! I love Mathematica. I knew my fella loved me when he got me that for my birthday one year. It meant he “got” me. Cheers! :^>

@waterskier2007: That’s odd. I’ve never heard diff eq referred to as Calc 4. Integration by parts is really useful. I hope you feel derustified now. :^>

idk. here we refer to it as that. i think its just cus in the sequence its the one after calc 3

It’s just that diff eq isn’t dependent on calc 3. You could just as easily take it after calc 2. You don’t have to have an understanding of the multi-variable stuff prior to understanding diff eq. What’s considered calc 5, 6, 7, ...? :^>

umm linear algebra is after diff eq i believe

The point is that there’s a lot of other math that’s not just the next “calc” class. Cheers!

eleventeen.