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@@ 23,7 +23,7 @@ Main purposes are to obtain the composition of two functions or to evaluate a fu 
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Be aware that you cannot directly substitute x by a literal number e.g. 2, but that you need a variable taking this value, e.g. by using 
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<code>\number{two}{2}</code> and <code>\substitute{f2}{f}{x}{two}</code>. 

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+<code>\number{two}{2}</code> and <code>\substitute{f2}{f}{x}{two}</code>.</div> 
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You can also normalize, expand, sort and calculate the <code>\derivative</code> and <code>\substitute</code> command. They take the same 
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