# Math Help - perpetual integration

1. ## perpetual integration

I have to integrate the following:

as you can see I have an answer - this is such a long problem - it's like an integration of an integration of an...
and the final answer gives a math error in the calculator.

I also get a value out of calculator of -7.169337845

2. Originally Posted by stealthmaths
I have to integrate the following:

as you can see I have an answer - this is such a long problem - it's like an integration of an integration of an...
and the final answer gives a math error in the calculator.

I also get a value out of calculator of -7.169337845

go to the link ... scroll down to the tabular method of integration by parts.

Integration by Parts

3. yes i know integration by parts.
I have done the integration but it is extremely long
it just keeps going into more integration by parts.
until i get the final values below.

but i'm not sure this is correct as it such a long solution.
i haven't put the workings here as i have an exam to revise for tomorrow and this also has to be handed in in the morning. it will take so long to input and i think it has gone wrong.

4. Originally Posted by stealthmaths
yes i know integration by parts.
I have done the integration but it is extremely long
it just keeps going into more integration by parts.
until i get the final values below.

but i'm not sure this is correct as it such a long solution.
i haven't put the workings here as i have an exam to revise for tomorrow and this also has to be handed in in the morning. it will take so long to input and i think it has gone wrong.
one more time ...
look at the section in the link titled tabular method

5. yes sorry skeeter. i was just looking at it.
very nice
i will try it now
thanks

6. ok. here it is. but I think I will loose marks for this method as we haven't been shown it yet.
But I like it! I like it a lot

7. sorry
sleeping whilst typing
could somebody check this for me please
thank you

8. Originally Posted by stealthmaths
sorry
sleeping whilst typing
could somebody check this for me please
thank you

Wrong. I got a different solution:

http://integrals.wolfram.com/index.jsp?expr=2x^3+e^-x&random=false

You forgot the x in the third multiplication and forgot to do the last multiplication. You also got half of signs wrong .
It's more like this.

$|-2e^{-x} x^3 - 6e^{-x} x^2 -12 e^{-x} x -12 e^{-x}|_{0}^{3}$

9. This is the solution worked out the integration by parts method. It is not checked yet though, so not sure if its right.