现代数值数学和计算习题答案(同济版)(19)

functiony=ex217

n=21;

x=linspace(-5,5,n)’;h=(5-(-5))/(n-1);y=1./(1+x.^2);

%formthedifferencestable

forj=2:n,

y(1:n+1-j,j)=diff(y(1:n+2-j,j-1))./(x(j:n)-x(1:n+1-j));end

%newtoncoeff

y=y(1,:);pz=[];

v=linspace(-5,5,80);fort=v,

z=y(n);

forj=n-1:-1:1,

z=z*(t-x(j))+y(j);end

pz=[pzz];end

plot(v,pz,’r+-’,v,1./(1+v.^2),’g--’);

:(

[ 4,4]

)

[ 2.5,2.5]60.

±4.8

,

4.

3

f(x)=(x+1)34:

2

1

20

?

xi=5cos(iπ/20),0≤i≤20,q(x).f(x)q(x)

x=linspace(-5,5,n)’;

19