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Solution set

From Wikipedia, the free encyclopedia

In mathematics, the solution set of a set of equations and inequalities is the set of all its solutions, that is the values that satisfy all equations and inequalities.[1]

If there is no solution, the solution set is the empty set.[2]

Examples

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  • The solution set of the single equation is the set {0}.
  • Since there do not exist numbers and making the two equations simultaneously true, the solution set of this system is the empty set .
  • The solution set of a constrained optimization problem is its feasible region.

Remarks

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In algebraic geometry, solution sets are called algebraic sets if there are no inequalities. Over the reals, and with inequalities, there are called semialgebraic sets.

Other meanings

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More generally, the solution set to an arbitrary collection E of relations (Ei) (i varying in some index set I) for a collection of unknowns , supposed to take values in respective spaces , is the set S of all solutions to the relations E, where a solution is a family of values such that substituting by in the collection E makes all relations "true".

(Instead of relations depending on unknowns, one should speak more correctly of predicates, the collection E is their logical conjunction, and the solution set is the inverse image of the boolean value true by the associated boolean-valued function.)

The above meaning is a special case of this one, if the set of polynomials fi if interpreted as the set of equations fi(x)=0.

Examples

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  • The solution set for E = { x+y = 0 } with respect to is S = { (a,−a) : aR }.
  • The solution set for E = { x+y = 0 } with respect to is S = { −y }. (Here, y is not "declared" as an unknown, and thus to be seen as a parameter on which the equation, and therefore the solution set, depends.)
  • The solution set for with respect to is the interval S = [0,2] (since is undefined for negative values of x).
  • The solution set for with respect to is S = 2πZ (see Euler's identity).

See also

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References

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  1. ^ "Definition of SOLUTION SET". www.merriam-webster.com. Retrieved 2024-08-14.
  2. ^ "Systems of Linear Equations". textbooks.math.gatech.edu. Retrieved 2024-08-14.