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Vieta's Substitution


The substitution of

 x=w-p/(3w)
(1)

into the standard form cubic equation

 x^3+px=q.
(2)

The result reduces the cubic to the equation

 w^3-(p^3)/(27w^3)-q=0,
(3)

which is easily turned into a quadratic equation in w^3 by multiplying through by w^3 to obtain

 (w^3)^2-q(w^3)-1/(27)p^3=0.
(4)

See also

Cubic Equation, Quadratic Equation

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Cite this as:

Weisstein, Eric W. "Vieta's Substitution." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/VietasSubstitution.html

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