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I encounter this problem in Mathematica 9.0.1, I'm not sure if it ever happens in other version.

Plot[{x, x + 1}, {x, 0, 10}, PlotStyle -> {Red, Green}]

This will show a red curve and a green curve, which is as expected.

But

Plot[{a, b} /. {a -> x, b -> x + 1}, {x, 0, 10}, PlotStyle -> {Red, Green}]

will give me two green curves.

Since

{a, b} /. {a -> x, b -> x + 1}

will give you

{x, 1 + x}

, I don't understand why there is difference in the results given by the two plot statements.

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  • $\begingroup$ mathematica.stackexchange.com/questions/11772/… $\endgroup$
    – ssch
    Mar 1, 2013 at 3:18
  • $\begingroup$ From the documentation: Plot has attribute HoldAll and evaluates f only after assigning specific numerical values to x. You need to Evaluate first. $\endgroup$
    – Matariki
    Mar 1, 2013 at 3:20

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