Reduce

Reduce[expr,vars]
reduces the statement expr by solving equations or inequalities for vars and eliminating quantifiers.

Reduce[expr,vars,dom]
does the reduction over the domain dom. Common choices of dom are Reals, Integers, and Complexes.

Details and OptionsDetails and Options

  • The statement expr can be any logical combination of:
  • lhs==rhsequations
    lhs!=rhsinequations
    or inequalities
    exprdomdomain specifications
    {x,y,}regregion specification
    ForAll[x,cond,expr]universal quantifiers
    Exists[x,cond,expr]existential quantifiers
  • The result of Reduce[expr,vars] always describes exactly the same mathematical set as expr.
  • Reduce[{expr1,expr2,},vars] is equivalent to Reduce[expr1&&expr2&&,vars].
  • Reduce[expr,vars] assumes by default that quantities appearing algebraically in inequalities are real, while all other quantities are complex.
  • Reduce[expr,vars,dom] restricts all variables and parameters to belong to the domain dom.
  • If dom is Reals, or a subset such as Integers or Rationals, then all constants and function values are also restricted to be real.
  • Reduce[expr&&varsReals,vars,Complexes] performs reductions with variables assumed real, but function values allowed to be complex.
  • Reduce[expr,vars,Integers] reduces Diophantine equations over the integers.
  • Reduce[,xreg,Reals] constrains x to be in the region reg. The different coordinates for x can be referred to using Indexed[x,i].
  • Reduce[expr,{x1,x2,},] effectively writes expr as a combination of conditions on , , where each condition involves only the earlier .
  • Algebraic variables in expr free of the and of each other are treated as independent parameters.
  • Applying LogicalExpand to the results of Reduce[expr,] yields an expression of the form , where each of the can be thought of as representing a separate component in the set defined by expr.
  • The may not be disjoint and may have different dimensions. After LogicalExpand, each of the has the form .
  • Without LogicalExpand, Reduce by default returns a nested collection of conditions on the , combined alternately by Or and And on successive levels.
  • When expr involves only polynomial equations and inequalities over real or complex domains, then Reduce can always in principle solve directly for all the .
  • When expr involves transcendental conditions or integer domains, Reduce will often introduce additional parameters in its results.
  • When expr involves only polynomial conditions, Reduce[expr,vars,Reals] gives a cylindrical algebraic decomposition of expr.
  • Reduce can give explicit representations for solutions to all linear equations and inequalities over the integers and can solve a large fraction of Diophantine equations described in the literature.
  • When expr involves only polynomial conditions over real or complex domains, Reduce[expr,vars] will always eliminate quantifiers, so that quantified variables do not appear in the result.
  • The following options can be given:
  • BacksubstitutionFalsewhether to give results unwound by backsubstitution  »
    CubicsFalsewhether to use explicit radicals to solve all cubics  »
    GeneratedParametersChow to name parameters that are generated  »
    Modulus0modulus to assume for integers  »
    QuarticsFalsewhether to use explicit radicals to solve all quartics  »
  • Reduce[expr,{x1,x2,},Backsubstitution->True] yields a form in which values from equations generated for earlier are backsubstituted so that the conditions for a particular have only minimal dependence on earlier . »
Introduced in 1988
(1.0)
| Updated in 2014
(10.0)