The symbol is used to denote a quantity which should be both added and subtracted, as in . The symbol can be used
to denote a range of uncertainty, or to denote a pair of quantities, such as the roots given by the Quadratic Formula

When order is relevant, the symbol is also used, so an expression of the form is interpreted as or . In contrast, the expression is interpreted to mean the set of four quantities , , , and .

© 1996-9

1999-05-25