Definition:Tschirnhaus Transformation

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Definition

Let $\map f x$ be a polynomial over a field $k$:

$\map f x = a_n x^n + a_{n - 1} x^{n - 1} + a_{n - 2} x^{n - 2} + \cdots + a_1 x + a_0$


Then the Tschirnhaus transformation is the linear substitution $x = y - \dfrac {a_{n - 1} } {n a_n}$.

The Tschirnhaus transformation produces a resulting polynomial $\map {f'} y$ which is depressed, as shown on Tschirnhaus Transformation yields Depressed Polynomial.

This technique is used in the derivation of Cardano's Formula for the roots of the general cubic.



Also known as

A Tschirnhaus transformation is also called a Tschirnhaus substitution.

Many sources refer to it as a Tschirnhausen transformation.


Also see

  • Results about Tschirnhaus transformations can be found here.


Source of Name

This entry was named for Ehrenfried Walther von Tschirnhaus.


Sources