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    $\[ \sum_{k=0}^{n} \binom{n}{k} = 2^n\] $

Do I need a special package, or is something else wrong with this?

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  • 3
    You had not insert display math environment inside inline math environment! Should be \[ \sum_{k=0}^{n} \binom{n}{k} = 2^n\].
    – Zarko
    Mar 31, 2022 at 15:22
  • 6
    you can not have \[ inside $ use $ for inline math or \[ for display math, not both.
    – David Carlisle
    Mar 31, 2022 at 15:22
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    also \binom is not defined by default, (comes from amsmath)
    – David Carlisle
    Mar 31, 2022 at 15:23
  • You wrote $ $$ \sum_{k=0}^n ... $$ $ which seems to be over complicated.
    – wipet
    Mar 31, 2022 at 19:31
  • thanks, to give some context the problem is it doent display it right when i pput $$, the limits of the sum are not above and below sigma , i dont know how to do this
    – Matko
    Apr 2, 2022 at 10:37

2 Answers 2

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It seems you are struggling with some very basic tasks of LaTeX. Please consider consulting an introductory text. You can find an exhaustive list here:

You are trying to nest displayed math inside inline math. This cannot work. You can only use one of the two at a time.

Display math is introduced by \[ ... \] whereas inline math is delimited by $ ... $. Without context it's hard to say which one is more appropriate here, but I guess it is display math (i.e. centered horizontally and on a separate line).

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\[ \sum_{k=0}^{n} \binom{n}{k} = 2^n \]

\end{document}

enter image description here

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  • Thanks for the quick answer.
    – Matko
    Apr 2, 2022 at 10:33
  • I did use latex some time ago, but i forgot even that little i knew in what now im 1000 lines in and i didnt know about this [] function.
    – Matko
    Apr 2, 2022 at 10:35
  • But its not what i need, cause i want the equation in a sentence so i need $$, but then it doesnt display the limits of the sum the same way, above the sigma symbol.
    – Matko
    Apr 2, 2022 at 10:36
  • @Matko That is on purpose, so that the vertical height of the sum doesn't open up the line too much. If you don't care about that you can use $\sum\limits_{k=0}^{n} \binom{n}{k} = 2^n$.
    – Henri Menke
    Apr 2, 2022 at 18:22
  • Oh yea that's what I wanted thanks.
    – Kugutsu-o
    Apr 3, 2022 at 19:48
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You can use the command \displaystyle in an inline expression (with $...$) to have equations displayed as in isolated math mode (the one you obtain with \[...\]).

In your example, it would be: $\displaystyle\sum_{k=0}^n \binom{n}{k} = 2^n$.

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    Your suggestion is possible, but not recommended. Using it lead to very poor typography. That is reason why latex has different formatting of in-line math from displayed ones. Also it not explain the OP problem.
    – Zarko
    Apr 5, 2022 at 16:14
  • According to the comments of OP, that was what he was trying to achieve by combining \[...\] and $...$. Though it is not proper typography, it can prove useful in some context, and it is the author decision to make.
    – pandamoniark
    Apr 6, 2022 at 11:56

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