matlab题：对于函数f（x）=1/（1+25x^2）,在区间[-1,1]上取Xi=-1+0.2*i（i=0,1,…,

i = 0:10;
x = -1+0.2*i;
y = 1./(1+25*x.^2);
p=polyfit(x,y,3);
s=vpa(poly2sym(p))
f = polyval(p,x);
plot( x,f,x,y,'o ')
三次曲线拟合结果：
s = -.18688658920776270929651442156525e-15*x^3-.57518273581621997911590671771667*x^2+.10642860455919865470368948113046e-15*x+.48412492484890679023123993829358