第四章 MATLAB的数值计算功能 Chapter 4: Numerical computation of MATLaB 、多项式( Polynomial 多项式的表达与创建( Expression and Creating of polynomia (1)多项式的表达( expression of polynomial) Maab用行矢量表达多项式系数 Coefficient,各元素按变量的降 幂顺序排列,如多项式为: P(x)=aox"+ajx -+a2x-2.an-1x+an 则其系数矢量 ectorof coefficient)为:P=|a0a1… an-1 an 如将根矢量( lector ofroc)表示为: ar=arar2…arnl 则根矢量与系数矢量之间关系为: (x-ar1)(x-ar2).(x-arn)=aox+ajx -+a2x -2...an-1x+an (2)多项式的创建( polynomial creating) a)系数矢量的直接输入法 利用poly2sym函数直接输入多项式的系数矢量,就可方便的建立 符号形式的多项式。 例:创建多项式x3-4x2+3x+2 poly 2sym([1-43 2]) ans x^3-4*x^2+3*x+2 POLY Convert roots to polynomial POLY(A), when a is an n by n matrix, is a row vector with N+l elements which are the coefficients of the characteristic polynomial, DET(lambda"EYE(SIZE(A))-A) POLY(V), when V is a vector, is a vector whose elements are the coefficients of the polynomial whose roots are the elements of v. for vectors rootS and poly are inverse functions of each other, up to ordering, scaling, and第四章 MATLAB 的数值计算功能 Chapter 4: Numerical computation of MATLAB 一、多项式(Polynomial)` 1．多项式的表达与创建(Expression and Creating of polynomial) (1) 多项式的表达（expression of polynomial）_ Matlab 用行矢量表达多项式系数(Coefficient)，各元素按变量的降 幂顺序排列，如多项式为： P(x)=a0x n+a1x n-1+a2x n-2…an-1x+an 则其系数矢量(Vector of coefficient)为：P=[a0 a1 … an-1 an] 如将根矢量(Vector of root)表示为： ar=[ ar1 ar2 … arn] 则根矢量与系数矢量之间关系为： （x-ar1）(x-ar2) … (x- arn)= a0x n+a1x n-1+a2x n-2…an-1x+an (2)多项式的创建（polynomial creating） a)系数矢量的直接输入法 利用 poly2sym 函数直接输入多项式的系数矢量，就可方便的建立 符号形式的多项式。 例：创建多项式 x 3 -4x2+3x+2 poly2sym([1 -4 3 2]) ans = x^3-4*x^2+3*x+2 POLY Convert roots to polynomial. POLY(A), when A is an N by N matrix, is a row vector with N+1 elements which are the coefficients of the characteristic polynomial, DET(lambda*EYE(SIZE(A)) - A) . POLY(V), when V is a vector, is a vector whose elements are the coefficients of the polynomial whose roots are the elements of V . For vectors, ROOTS and POLY are inverse functions of each other, up to ordering, scaling, and