Posted by xX_Supaman_Xx on Saturday, December 29, 2007 at 9:45pm.
hey guys,
i follow you up to the point of intergrating the final line. How would I intergrate [x^2.e^x] dx
thx

drwls & Damon  maths  drwls, Sunday, December 30, 2007 at 10:20am
My first suggestion was to try the method of "integration by parts", but that may not work. I found a recursion formula for the integral in my Table of Integrals, but it ends up requiring the integral of e^x/x , which is a new fucntion called the exponential integral, Ei(x). Perhaps I made a mistake somewhere applying the "integrating factor" method. Damon has made more progress and is better equipped to help you. I am giving up on it

drwls & Damon  maths  Damon, Sunday, December 30, 2007 at 1:55pm
Yes, use the recursion formula. You need it later to cancel the next term.
in general:
int e^ax dx/x^n = (1/(n1)) [e^ax/x^(n1) + a int e^ax/x^(n1)dx] for n integergreater than one
here n is two
so here I had:
y e^x/x=int( e^x dx/x)(1/x + 1)dx + C
ye^x/x =int e^x dx/x^2 + int e^x dx/x
+C
ye^x / x = (1/1)[e^x/x  int e^x dx/x ] + e^x dx/x +C
see that gets rid of the int e^x dx/x terms and you are left with
y e^x/x = e^x/x + C
y = 1 + x C / e^x
y = x C e^x  1 :)

drwls & Damon  maths  Damon, Sunday, December 30, 2007 at 2:00pm
Typo:
ye^x / x = (1/1)[e^x/x  int e^x dx/x ] + INTEGRAL e^x dx/x +C
see that gets rid of the int e^x dx/x terms and you are left with
Answer This Question
Related Questions
 trigonometry  Find the distance using the appropriate arch length. A television...
 English  umm don't know if i'm able to ask this but i was wondering if you guys...
 physics  DAMON  a +35x10^6 C point charge is placed 32 cm from an identical +...
 Thx again for another year of success  Hey ms. sue, i am now in 9th grade thx ...
 maths  The line segment connecting A(18,8) and B(10,8) is divided in the ...
 History  Hey I need to know how the government controls oil. Can you help me? ...
 physics hey damon one more please! =]  Consider a spaceship located on the ...
 physics  hey you guys , i reay appreciate it if you guys help me out . Q: a ...
 English  Hey guys, I was just wondering if you could help me find or explain to...
 Agricultural,maths Literacy,consumer studies and Geography  Guys i just want to...
More Related Questions