operators within the dollar sign

I am using operators : +,-. For example, $6-1$. The operator - becomes rather large between .

Normally, would you leave the operator negative between the ? If not, how do you make it to the normal size ?

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Welcome to TeX.SE. Are you referring to the size of the operator, or to the spacing on either side? The size and spacing that $6-1$ produces is considered the correct math spacing. The minus should definitely be within the dollar signs as long as it is minus operation. – Peter Grill Nov 21 '12 at 3:52
Thanks for the comments. I was wrong. I was putting the minus sign outside. – Asha Nov 21 '12 at 4:03

Since you're referring to - in the mathematical context, use it as such in (La)TeX. So, use $-i$ instead of -$i$. Use $k+p$ instead of $k$+$p$. Here are some examples of the output:

\documentclass{article}
\begin{document}
If I use -$i$, the spacing around the symbol and operator is not correct.
Compare this to $-i$.
Also, when using these operators in a binary sense, it should be used as $k+p$, and not $k$+$p$.

\begin{center}
\begin{tabular}{cc}
Wrong & Correct \\ \hline
-$i$ & $-i$ \\
$k$+$p$ & $k+p$
\end{tabular}
\end{center}
\end{document}

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Thanks for all the comments. I was putting the minus sign outside which is wrong. I would correct it now. – Asha Nov 21 '12 at 4:02