# Unexpected additional value in output of integral

Posted 15 days ago
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 Hi; In calculating an integral (using both the icon from the Classroom Pallett and the Integrate[] function in Mathematica) , it appears that Mathematica is placing an additional value in the results that is both unexpected and unwanted (see attached for full explanation). Possibly, there is something that I am not understanding about the Integrate command, so please help me understand what I am doing incorrectly, or why Mathematica is placing the extra value that I don't seem to need.Thank you so much,Mitchell Sandlin Attachments: Answer
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Posted 14 days ago
 Strange! No idea.Look at Simplify[Integrate[(x^2 - 3 x + 2)/(x + 1), {x, 0, xx}] /. xx -> x, x > -1] // Expand Answer
Posted 14 days ago
 This simply is because Integrate in this way gives an antiderivative - and an antiderivative is always determined up to some arbitrary constant. Answer
Posted 14 days ago
 Hallo Henrik,clear, but why - 9 / 2 and not some constant, e.g. like C ?And for example Integrate[ (x + 2)/(x + 1), x] does nothing like that Gruß Hans Answer
Posted 14 days ago
 And look at this !? p[n_] := Sum[a[j] x^j, {j, 0, n}] Table[(Integrate[p[n]/(1 + x), x] // Expand) /. x -> 0, {n, 0, 15}] and Table[(Integrate[p[n]/(1 + x) /. a[n] -> 1, x] // Expand) /. x -> 0, {n, 0, 15}] Answer
Posted 14 days ago
 I gave the integral to Wolfram|Alpha with step-by-step integration. The constant - 9 / 2 appears out of nowhere in the final result, together with "+constant". I suppose it comes from the internals of the Risch algorithm, which is far from the way a human would normally do. Answer