I want to build a function that returns an expression "canceled". There goes my code.
SetAttributes[cancel,HoldFirst];
cancel[expr_]:= Show[
Graphics[{
{Arrowheads[{.04}],Arrow[{{-0.0001,-0.0001},{0.0001,0.0001}}]},
{Text[expr]}
}], ImageSize-> Tiny,BaselinePosition-> Bottom];
Divide[Row[{cancel[""(x-a)],x^n}],Row[{""(x^2+7),cancel[""(x-a)]}]]

The coordinates of Arrow are not working (I thing).
Am I missing something?
Is there a better way to make the same thing?
Does Mathematica have some similar procedure?
Thanks
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