Root
 Usage
• Root[f, k] represents the k root of the polynomial equation f[x]  0.
Notes
• f must be a Function object such as (#^5 - 2 # + 1)&. • Root[f, k] is automatically reduced so that f has the smallest possible degree and smallest integer coefficients. • The ordering used by Root takes real roots to come before complex ones, and takes complex conjugate pairs of roots to be adjacent. • The coefficients in the polynomial f[x] can involve symbolic parameters. • For linear and quadratic polynomials f[x], Root[f, k] is automatically reduced to explicit rational or radical form. • N finds the approximate numerical value of a Root object. • Operations such as Abs, Re, Round and Less can be used on Root objects. • Root[f, k] is treated as a numeric quantity if f contains no symbolic parameters. • Root by default isolates the roots of a polynomial using approximate numerical methods. No cases are known where this approach fails. SetOptions[Root, ExactRootIsolation->True] will however make Root use much slower but fully rigorous methods. • New in Version 3.
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