Solve
Solve[expr,vars]
attempts to solve the system expr of equations or inequalities for the variables vars.
Details and Options
 The system expr can be any logical combination of:

lhs==rhs equations lhs!=rhs inequations lhs>rhs or lhs>=rhs inequalities expr∈dom domain specifications {x,y,…}∈reg region specification ForAll[x,cond,expr] universal quantifiers Exists[x,cond,expr] existential quantifiers  Solve[{expr_{1},expr_{2},…},vars] is equivalent to Solve[expr_{1}&&expr_{2}&&…,vars].
 A single variable or a list of variables can be specified.
 Solve gives solutions in terms of rules of the form:

{} no solutions {{x>sol_{x},y>sol_{y},…},…} several solutions {{}} solution set is full dimensional  When a single variable is specified and a particular root of an equation has multiplicity greater than one, Solve gives several copies of the corresponding solution.
 Solve[expr,vars] assumes by default that quantities appearing algebraically in inequalities are real, while all other quantities are complex.
 Solve[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.
 Solve[expr&&vars∈Reals,vars,Complexes] solves for real values of variables, but function values are allowed to be complex.
 Solve[expr,vars,Integers] solves Diophantine equations over the integers.
 Solve[…,x∈reg,Reals] constrains x to be in the region reg. The different coordinates for x can be referred to using Indexed[x,i].
 Algebraic variables in expr free of the and of each other are treated as independent parameters.
 Solve deals primarily with linear and polynomial equations.
 When expr involves only polynomial equations and inequalities over real or complex domains, then Solve can always in principle solve directly for all the .
 When expr involves transcendental conditions or integer domains, Solve will often introduce additional parameters in its results.
 Solve 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, Solve[expr,vars] will always be able to eliminate quantifiers.
 Solve gives generic solutions only. Solutions that are valid only when continuous parameters satisfy equations are removed. Other solutions that are only conditionally valid are expressed as ConditionalExpression objects.
 Conditions included in ConditionalExpression solutions may involve inequalities, Element statements, equations and inequations on noncontinuous parameters, and equations with fulldimensional solutions. Inequations and NotElement conditions on continuous parameters and variables are dropped.
 Solve uses nonequivalent transformations to find solutions of transcendental equations and hence it may not find some solutions and may not establish exact conditions on the validity of the solutions found.
 Solve uses special efficient techniques for handling sparse systems of linear equations with approximate numerical coefficients.
 The following options can be given:

Cubics False whether to use explicit radicals to solve all cubics GeneratedParameters C how to name parameters that are generated InverseFunctions Automatic whether to use symbolic inverse functions MaxExtraConditions 0 how many extra equational conditions on continuous parameters to allow Method Automatic what method should be used Modulus 0 modulus to assume for integers Quartics False whether to use explicit radicals to solve all quartics VerifySolutions Automatic whether to verify solutions obtained using nonequivalent transformations WorkingPrecision Infinity precision to be used in computations  With MaxExtraConditions>Automatic, only solutions that require the minimal number of equational conditions on continuous parameters are included.
 With MaxExtraConditions>All, solutions that require arbitrary conditions on parameters are given and all conditions are included.
 With MaxExtraConditions>k, only solutions that require at most k equational conditions on continuous parameters are included.
 With Method>Reduce, Solve uses only equivalent transformations and finds all solutions.
 Solve[eqns,…,Modulus>m] solves equations over the integers modulo m. With Modulus>Automatic, Solve will attempt to find the largest modulus for which the equations have solutions.
Examples
open allclose allBasic Examples (5)
Scope (73)
Basic Uses (6)
Solutions are given as lists of replacements:
Use ReplaceAll (/.) to replace by solutions:
Check that solutions satisfy the equations:
Solve uses {} to represent the empty solution or no solution:
Solve uses {{}} to represent the universal solution or all points satisfying the equations:
Find solutions over specified domains:
Solve equations with coefficients involving a symbolic parameter:
Plot the real parts of the solutions for y as a function of the parameter a:
Solution of this equation over the reals requires conditions on the parameters:
Replace x by solutions and simplify the results:
Use Normal to remove the conditions:
Solution of this equation over the positive integers requires introduction of a new parameter:
Complex Equations in One Variable (11)
Polynomial equations solvable in radicals:
Polynomial equations with multiple roots:
Polynomial equations with symbolic coefficients:
Univariate elementary function equations over bounded regions:
Univariate holomorphic function equations over bounded regions:
Here Solve finds some solutions but is not able to prove there are no other solutions:
Equation with a purely imaginary period over a vertical stripe in the complex plane:
Systems of Complex Equations in Several Variables (8)
Real Equations in One Variable (13)
Polynomial equations with multiple roots:
Polynomial equations with symbolic coefficients:
Transcendental equations, solvable using inverse functions:
Transcendental equations, solvable using special function zeros:
Transcendental inequalities, solvable using special function zeros:
Highdegree sparse polynomial equations:
Algebraic equations involving highdegree radicals:
Equations involving nonrational real powers:
Tame elementary function equations:
Elementary function equations in bounded intervals:
Holomorphic function equations in bounded intervals:
Systems of Real Equations and Inequalities in Several Variables (9)
Quantified polynomial systems:
Transcendental systems, solvable using inverse functions:
Systems explog in the first variable and polynomial in the other variables:
Systems elementary and bounded in the first variable and polynomial in the other variables:
Systems holomorphic and bounded in the first variable and polynomial in the other variables:
Diophantine Equations (11)
Modular Equations (4)
Systems with Mixed Variable Domains (2)
Options (15)
Cubics (1)
GeneratedParameters (1)
Solve may introduce new parameters to represent the solution:
Use GeneratedParameters to control how the parameters are generated:
InverseFunctions (3)
By default, Solve uses inverse functions but prints warning messages:
For symbols with the NumericFunction attribute, symbolic inverses are not used:
With InverseFunctions>True, Solve does not print inverse function warning messages:
Symbolic inverses are used for all symbols:
With InverseFunctions>False, Solve does not use inverse functions:
Solving algebraic equations does not require using inverse functions:
Here, a method based on Reduce is used, as it does not require using inverse functions:
MaxExtraConditions (4)
By default, no solutions requiring extra conditions are produced:
Unless the parameters are discrete:
The default setting, MaxExtraConditions>0, gives no solutions requiring conditions:
MaxExtraConditions>1 gives solutions requiring up to one equation on parameters:
MaxExtraConditions>2 gives solutions requiring up to two equations on parameters:
Give solutions requiring the minimal number of parameter equations:
By default, Solve drops inequation conditions on continuous parameters:
With MaxExtraConditions>All, Solve includes all conditions:
Method (1)
Modulus (2)
Quartics (1)
VerifySolutions (1)
Solve verifies solutions obtained using nonequivalent transformations:
With VerifySolutions>False, Solve does not verify the solutions:
Some of the solutions returned with VerifySolutions>False are not correct:
This uses a fast numeric test in an attempt to select correct solutions:
In this case numeric verification gives the correct solution set:
WorkingPrecision (1)
By default, Solve finds exact solutions of equations:
Computing the solution using 100digit numbers is faster:
The result agrees with the exact solution in the first 100 digits:
Computing the solution using machine numbers is much faster:
Applications (6)
Find intersection points of a circle and a parabola:
Find conditions for a quartic to have all roots equal:
A method using Subresultants:
A method using quantifier elimination:
Plot a space curve given by an implicit description:
Plot the projection of the space curve on the {x,y} plane:
Find a sequence of Pythagorean triples:
Find how to pay $2.27 postage with 10, 23, and 37cent stamps:
The same task can be accomplished with IntegerPartitions:
Properties & Relations (13)
Solutions satisfy the equations:
Solutions are given as replacement rules and can be directly used for substitution:
Solve uses {} to represent the empty solution or no solution:
Solve uses {{}} to represent the universal solution or all points satisfying the equations:
For univariate equations, Solve repeats solutions according to their multiplicity:
Solutions of algebraic equations are often given in terms of Root objects:
Use N to compute numeric approximations of Root objects:
Root objects may involve parameters:
Use Series to compute series expansions of Root objects:
The series satisfies the equation up to order 11:
Solve represents solutions in terms of replacement rules:
Reduce represents solutions in terms of Boolean combinations of equations and inequalities:
Solve uses fast heuristics to solve transcendental equations, but may give incomplete solutions:
Reduce uses methods that are often slower, but finds all solutions and gives all necessary conditions:
Use FindInstance to find solution instances:
Like Reduce, FindInstance can be given inequalities and domain specifications:
Use DSolve to solve differential equations:
Use RSolve to solve recurrence equations:
SolveAlways gives the values of parameters for which complex equations are always true:
The same problem can be expressed using ForAll and solved with Solve or Reduce:
Resolve eliminates quantifiers, possibly without solving the resulting quantifierfree system:
Eliminate eliminates variables from systems of complex equations:
This solves the same problem using Resolve:
Reduce and Solve additionally solve the resulting equations:
Possible Issues (4)
Solve gives generic solutions; solutions involving equations on parameters are not given:
Reduce gives all solutions, including those that require equations on parameters:
With MaxExtraConditions>All, Solve also gives nongeneric solutions:
Solve results do not depend on whether some of the input equations contain only parameters. The following two systems are equivalent and have no generic solutions:
Use MaxExtraConditions to specify the number of parameter conditions allowed:
Use the Exists quantifier to find solutions that are valid for some value of parameter :
Solve does not eliminate solutions that are neither generically correct nor generically incorrect:
The solutions are correct for and incorrect for :
For transcendental equations, Solve may not give all solutions:
Use Reduce to get all solutions:
Solve with Method>"Reduce" uses Reduce to find solutions, but returns replacement rules:
Using inverse functions allows Solve to find some solutions fast:
Finding the complete solution may take much longer, and the solution may be large: