Parentheses are used in mathematics to indicate that certain computations should precede other computations, and also to shorten expressions by virtue of the "distributive law" that says A x (B+C) = (A x B) + (A x C). Both of these uses can be applied to English text.
Golomb, Solomon W.
"Using Mathematical Parentheses in English,"
Word Ways: Vol. 40
, Article 21.
Available at: http://digitalcommons.butler.edu/wordways/vol40/iss2/21