This is documentation for Mathematica 6, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.2)


is an option for functions such as Simplify, Refine and Integrate which specifies default assumptions to be made about symbolic quantities.
  • The assumptions can be equations, inequalities or domain specifications, or lists or logical combinations of these.
  • xReals can be used to specify that x should be treated as a real variable.
  • Quantities that appear algebraically in inequalities are always assumed to be real.
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