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Re: Query regarding Function

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  • Subject: [mg130142] Re: Query regarding Function
  • From: Alexei Boulbitch <Alexei.Boulbitch at>
  • Date: Thu, 14 Mar 2013 07:12:49 -0400 (EDT)
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Dear all,

Case1:  In the following code


 The output is found to be  b^2+2 xy

Case2:  But for the code


 The output is 2 a+b^2

 Hence my query is why in case 1 x*y is not replaced by b and a whereas in case 2 it got replaced ?


Hi, Rahul,

Mathematica understands xy as a single new symbol, and, therefore, it does not interpret it as a product. If you want it to be multiplication you should make a space between x and y.
Then it works. Compare: this is your function

Clear[f, x, y]
g = Function[{x, y}, x^2 + 2 xy][b, a]

b^2 + 2 xy

and this is the same, but with the space between x and y:

Clear[f, x, y]
g = Function[{x, y}, x^2 + 2 x y][b, a]

2 a b + b^2

However, I prefer to put the sign "*" between x and y. Since it becomes quite clear from the first glance, what is x*y. Like this:

Clear[f, x, y]
g = Function[{x, y}, x^2 + 2 x*y][b, a]

2 a b + b^2

Have fun, Alexei


Alexei BOULBITCH, Dr., habil.
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e-mail: alexei.boulbitch at

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