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Learning about the formal definition of the derivativ, I am asked to find the derivative at the indicated point from the graph of the function.

However in the following problems, I do not understand what the ";"-symbol mean

f(x)=5;x=1

f(x)=4x-3;x=-1

Of course the meaning of ; is something I should remember, but any help would be much appreciated as google search and lists of mathematical symbols didn't help!

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    $\begingroup$ Where did you find such a notation...? $\endgroup$ – Megadeth Oct 19 '15 at 9:47
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    $\begingroup$ My previous guess at the meaning was wrong, so I deleted that comment. The question is asking you to calculate the derivative of the function that's written before the semicolon and then to evaluate that derivative at the value of $x$ that's written after the semicolon. $\endgroup$ – Andreas Blass Oct 19 '15 at 9:52
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    $\begingroup$ Following @AndreasBlass I suspect that the ";" is not mathematical but belongs to the "surrounding" natural language $\endgroup$ – Hagen von Eitzen Oct 19 '15 at 9:56
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It seems that it want the derivative of the given function at the point with a given $x$. So $f(x)=5 ; x=1$ means $f'(1)$ where $f'$ is the derivative of $f(x)=5$, and $f(x)=4x-3 ; x=-1$ means $f'(-1)$ where $f'$ is the derivative of $f(x)=4x-3$.

So,here, the symbol ''$;$'' is not really a mathematical symbol, but simply a punctuation mark.

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