MATLAB之roots 函数介绍（多项式根）

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roots
# Y0 L; R, h- F3 N- m$ L( FPolynomial roots
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Syntax
r = roots(p)

Description
r = roots（p）返回由p表示的多项式的根作为列向量。

输入p是包含n + 1个多项式系数的向量，从x^n的系数开始。
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系数0表示在等式中不存在的中间功率。

For example, p = [3 2 -2]represents the polynomial 3x^2+2x−2.
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/ U, T8 r! @  ~  W9 Z根函数解决了形式为p_1x^n+p_2x^{n-1}+...+p_nx^{n}+p_{n+1}=0的多项式方程.
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多项式方程包含具有非负指数的单个变量。
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Roots of Quadratic Polynomial
Solve the equation  3x^2 - 2x -4 = 0.
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3 t$ d( z. V6 I4 J* U, k& w* }Create a vector to represent the polynomial, then find the roots.

p = [3 -2 -4];
r = roots(p)
r = 2×1
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    1.5352
3 R' V8 F6 C8 m! R   -0.8685
  `8 ^) `# a' X- ~; v8 Y* g3 `Roots of Quartic Polynomial
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Solve the equationx^4-1=0 .
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4 n: S3 u9 ]5 y- _Create a vector to represent the polynomial, then find the roots.

  |$ j/ m* D+ Jp = [1 0 0 0 -1];
r = roots(p)
r = 4×1 complex

  -1.0000 + 0.0000i
  K) [8 P: O3 R7 m) l; V   0.0000 + 1.0000i
) H5 U& Y8 c1 H" a! q2 b) q/ a   0.0000 - 1.0000i
   1.0000 + 0.0000i
' `; b3 i; W# I( CInput Arguments
p — Polynomial coefficients
7 x/ a' T2 p) S& r/ M7 {9 Bvector
  l( M2 g% Q1 n! b' Z' J" }' ePolynomial coefficients, specified as a vector. For example, the vector [1 0 1] represents the polynomial x^2+1, and the vector [3.13 -2.21 5.99]represents the polynomial 3.13x^2−2.21x+5.99.

Data Types: single | double
Complex Number Support: Yes

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Tips
8 L/ W+ W& @) [Use the poly function to obtain a polynomial from its roots: p = poly(r). The poly function is the inverse of the roots function.
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MATLAB之poly 函数介绍

; n. I8 i% N4 P7 o3 I5 y' kUse the fzero function to find the roots of nonlinear equations. While the roots function works only with polynomials, the fzero function is more broadly applicable to different types of equations.

( @. l% p2 S  b+ U6 |+ B在MATLAB命令窗口中输入：doc fzero 查看fzero的相关介绍。

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MATLAB之roots 函数介绍（多项式根）