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Equations

An equation is the problem of finding values of some variable, called unknown, for which the specified equality is true. Each value of the unknown for which the equation holds is called a solution of the given equation; also stated as satisfying the equation. For example, the equation x 2 − 6 x + 5 = 0 {\displaystyle x^{2}-6x+5=0} has the values x = 1 {\displaystyle x=1} and x = 5 {\displaystyle x=5} as its only solutions. The terminology is used similarly for equations with several unknowns.

An equation can be used to define a set. For example, the set of all solution pairs (x, y) {\displaystyle (x,y)} of the equation x 2 + y 2 = 1 {\displaystyle x^{2}+y^{2}=1} forms the unit circle in analytic geometry; therefore, this equation is called the equation of the unit circle.

See also: Equation solving