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Integration

Hi, just wondering what integration technique you would use to integrate this to keep it simple, avoiding expanding the brackets. This is because it should cancel down to something simple and it gets incredibly messy once brackets are expanded.

I think it should cancel to h_ j / 6 but i can't seem to get it:

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Reply 1
Won't let me edit the post: This is the problem
I'd start off by writing the second bracket as:
1Xj+1Xhj=hjhjhj+XjXhj=XXjhj\displaystyle 1-\frac{X_{j+1}-X}{h_j}=\frac{h_j}{h_j}-\frac{h_j+X_j-X}{h_j}=\frac{X-X_j}{h_j}
Reply 3
Original post by rayquaza17
I'd start off by writing the second bracket as:
1Xj+1Xhj=hjhjhj+XjXhj=XXjhj\displaystyle 1-\frac{X_{j+1}-X}{h_j}=\frac{h_j}{h_j}-\frac{h_j+X_j-X}{h_j}=\frac{X-X_j}{h_j}



Thank you i've got it now :smile:
Original post by MaloneJ
Hi, just wondering what integration technique you would use to integrate this to keep it simple, avoiding expanding the brackets. This is because it should cancel down to something simple and it gets incredibly messy once brackets are expanded.

I think it should cancel to h_ j / 6 but i can't seem to get it:

Attachment not found


I've just had a look but can't get it myself either as once you sub in hj = whatever it was, you get into a mess which I can't get myself out of!

I have a gut feeling that integration by partial fractions may come into it, but then again I might be wrong!
Original post by spotify95
I've just had a look but can't get it myself either as once you sub in hj = whatever it was, you get into a mess which I can't get myself out of!
I have a gut feeling that integration by partial fractions may come into it, but then again I might be wrong!

We are integrating wrt x, and I think the hjh_j and Xj+1X_{j+1} are constants that don't depend on x. So I don't think it's anything more complicated than integrating something like ax and (xa)2(x-a)^2.
Original post by rayquaza17
We are integrating wrt x, and I think the hjh_j and Xj+1X_{j+1} are constants that don't depend on x. So I don't think it's anything more complicated than integrating something like ax and (xa)2(x-a)^2.


Okay, thank you for the help. :smile:

I give up on this, at least the OP's got it :wink:
Reply 7
Original post by spotify95
Okay, thank you for the help. :smile:

I give up on this, at least the OP's got it :wink:



Incase you were interested:



Thanks for the help
Original post by MaloneJ
Incase you were interested:



Thanks for the help


Thank you! :smile: There was no way I was getting that! :biggrin:

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