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Bézout's Theorem


Bézout's theorem for curves states that, in general, two algebraic curves of degrees m and n intersect in m·n points and cannot meet in more than m·n points unless they have a component in common (i.e., the equations defining them have a common factor; Coolidge 1959, p. 10).

Bézout's theorem for polynomials states that if P and Q are two polynomials with no roots in common, then there exist two other polynomials A and B such that AP+BQ=1. Similarly, given N polynomial equations of degrees n_1, n_2, ...n_N in N variables, there are in general n_1n_2...n_N common solutions.

Séroul (2000, p. 10) uses the term Bézout's theorem for the following two theorems.

1. Let a,b in Z be any two integers, then there exist u,v in Z such that

 au+bv=GCD(a,b).

2. Two integers a and b are relatively prime if there exist u,v in Z such that

 au+bv=1.

See also

Blankinship Algorithm, Greatest Common Divisor, Polynomial

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References

Coolidge, J. L. A Treatise on Algebraic Plane Curves. New York: Dover, p. 10, 1959.Séroul, R. "The Bézout Theorem." §2.4.1 in Programming for Mathematicians. Berlin: Springer-Verlag, p. 10, 2000.Shub, M. and Smale, S. "Complexity of Bézout's Theorem. I. Geometric Aspects." J. Amer. Math. Soc. 6, 459-501, 1993.Shub, M. and Smale, S. "Complexity of Bézout's Theorem. II. Volumes and Probabilities." In Computational Algebraic Geometry (Nice, 1992). Boston, MA: Birkhäuser, pp. 267-285, 1993.Shub, M. and Smale, S. "Complexity of Bézout's Theorem. III. Condition Number and Packing." J. Complexity 9, 4-14, 1993.Shub, M. and Smale, S. "Complexity of Bézout's Theorem. IV. Probability of Success; Extensions." SIAM J. Numer. Anal. 33, 128-148, 1996.Shub, M. and Smale, S. "Complexity of Bézout's Theorem. V. Polynomial Time." Theoret. Comput. Sci. 134, 141-164, 1994.

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Bézout's Theorem

Cite this as:

Weisstein, Eric W. "Bézout's Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BezoutsTheorem.html

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