Please, can anybody help me to find the answer of this integration.

Questions
,
1

Integrate[(x - Subscript[x, i])^2 (x - Subscript[x, i + 1])^2, {x,
Subscript[x, i - 1], Subscript[x, i + 1]}]

Please i Need help to get this answer, i’ll be very thankful.

the answer is:

-1/30 (Subscript[x,i-1]-Subscript[x,i+1])^3 (6(Subscript[x,i-1])^2+10(Subscript[x,i])^2-5(Subscript[x,i])(Subscript[x,i+1])+(Subscript[x,i+1])^2-15Subscript[x,i-1]Subscript[x,i]+3Subscript[x,i-1]Subscript[x,i+1])
2

Hi,

the issue is how Mathematica handles indices. This might be useful:

Hope this helps,
M.

3

Hi,

… and one might add that the integration itself works perfectly if it is done in a clean way:

Clear[x, a, b, c];
Integrate[(x - a)^2 (x - c)^2, {x, b, c}] /. {a -> Subscript[x, i], b -> Subscript[x, i - 1], c -> Subscript[x, i + 1]}

@Marco: Thanks for this interesting link!

Henrik

4

That is really grateful Henrik
Thanks a lot