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Finding Roots

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Topology, Calculus and Approximation

Part of the book series: Springer Undergraduate Mathematics Series ((SUMS))

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Abstract

Since Descartes’s groundbreaking work the exact or numerical solution of polynomial equations has become a frequent task in analytical geometry. We also have to find the roots of orthogonal polynomials for the implementation of the Gauss rules of numerical integration. Based on his differential calculus, Newton invented a powerful method for localizing the roots of twice differentiable functions.

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Notes

  1. 1.

    After the removal of its zero elements. For example, the sequence 1, 3, −2, 0, 1, −4 has 3 sign changes.

  2. 2.

    For example, when p is the characteristic polynomial of a symmetric matrix.

  3. 3.

    It can be computed by the Euclidean algorithm.

  4. 4.

    Notice the sign change for the remainders.

  5. 5.

    We consider the usual Euclidean norm on \(\mathbb{R}^{m}\).

  6. 6.

    The matrices H(v) are symmetric, but we do not need this property here.

  7. 7.

    See the remark following the statement of the proposition.

  8. 8.

    The spectrum of a matrix is by definition the set of its eigenvalues.

  9. 9.

    We will find that A has n distinct (real) eigenvalues in this case.

  10. 10.

    See also the second remark following the proof of Proposition  9.4.

  11. 11.

    See Exercise 11.3 for a more general result, p. 281.

  12. 12.

    The more general condition “f′ ≠ 0 and f″ ≠ 0 in [a, b]” may be reduced to this one by replacing f(x) with f(−x), − f(x) or − f(−x).

  13. 13.

    A convergence of this kind is called quadratic.

  14. 14.

    Compare to the example on p. 280.

  15. 15.

    Properties (ii) and (iii) will be improved in Exercise  12.3, p. 295.

  16. 16.

    See Exercise  12.3 for the real case.

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Komornik, V. (2017). Finding Roots. In: Topology, Calculus and Approximation. Springer Undergraduate Mathematics Series. Springer, London. https://doi.org/10.1007/978-1-4471-7316-8_11

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