Showing result of derivative and other functions [closed]

I have a problem with my Mathematica 7.0 When I write:

Derivative[x^2, x]


Mathematica returns as result :

Derivative[x^2, x]


not 2x

Why is that? Am I doing something wrong with Derivative?

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closed as off-topic by Artes, Sjoerd C. de Vries, Kuba, bobthechemist, rm -rf♦Jan 9 at 15:02

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• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – Artes, Sjoerd C. de Vries, Kuba, bobthechemist, rm -rf
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Reference here –  Sektor Jan 9 at 12:26
Use D[x^2, x] or Derivative[1][#^2 &][x]. –  Artes Jan 9 at 12:29

D[x^2, x]

Derivative is a representation when the derivative cannot be computed explicitly. For instance look at this example with an unknown function f
D[f[x],x]//FullForm