imaginary unit

In mathematics, the imaginary unit (or sometimes the Latin or the Greek iota, see below) allows the real number system to be extended to the complex number system . Its precise definition is dependent upon the particular method of extension.The primary motivation for this extension is the fact that not every polynomial equation with real coefficients has a solution in the real numbers. In particular, the equation has no real solution (see "Definition", below). However, if we allow complex numbers as solutions, then this equation, and indeed every polynomial equation does have a solution. (See algebraic closure and fundamental theorem of algebra.)
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