I guess I do not understand how Mathematica evaluates this simple expression inside FreeQ

a = 2 I
FreeQ[a, I]
FreeQ[2 I, I]
FreeQ[I, I]

(* 2 I *)
(* True *)
(* True *)
(* False *)
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    $\begingroup$ Check FullForm[a] or FullForm[ I ], etc. There are a lot of questions in the site about complex numbers an some ideas about how to cope with the difficulties that arise when trying to match them $\endgroup$ – Dr. belisarius Jun 29 '15 at 4:08
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    $\begingroup$ FreeQ[...,Complex]... $\endgroup$ – ciao Jun 29 '15 at 4:17
  • 2
    $\begingroup$ Thank you, FreeQ[..., Complex] works just fine. $\endgroup$ – Peter Jun 29 '15 at 4:23
  • 3
    $\begingroup$ If you want to check the form of the expression as you entered it, you can do FreeQ[HoldForm[2 I], HoldPattern[I]]. $\endgroup$ – Simon Rochester Jun 29 '15 at 4:39

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