When writing mathematics, punctuation should be placed in equations at the points where punctuation would occur if the equation was converted to text, as though spoken.

For display equations, punctuation must be placed inside the equation delimiters (\[...\] or $$...$$). <!–

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.code-output-container .output-block { background-color: #fff; }

</style>

Code: 

Although we expected
Output:

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For in-line equations in LaTeX documents, it is slightly preferable to put punctuation marks should be placed outside the math delimiters, e.g., “The minimum is located at $1/x$.” instead of “The minimum is located at $1/x.$”, since placing the punctuation inside an inline equation causes it to be formatted using a math font and math spacing, which might be noticeably different. LaTeX is clever enough to not insert a line break between an inline equation and punctuation that is immediately after.