[?] Get identical symbolic expressions after simplifying them differently?

Questions
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1

Dear Community,
I have two complicated functions, one stated as x1, the other as x2. Technically, they are the same (albeit simplified differently). When I subtract x2 from x1, I expect to get zero, but that does not happen. Can you please let me know what I am doing wrong? Thank you. P.S. The file is attached.

problem.nb (10.1 KB)

2

Mathematica does not extract symbolic factors from integrals. You can force it to do it:

extractConstants = (Integrate[a_*b_, {u_, lmts__}] /; FreeQ[a, u]) :> 
   a*Integrate[b, {u, lmts}];
Simplify[x1 - x2 //. extractConstants]
3

Thank you very much.