function iy=Horner3(n,a,c,x)
% 用Horner方法计算多项式的定积分
% Input:  n - 多项式次数
%         a - 多项式从低到高系数，长度为(n+1)的向量
%         c - 积分常数
%         x - 独立变量，求多项式在该点的值

%  NUMERICAL METHODS: Matlab Programs
% (c) 2007 by Xie Liling
%  Complementary Software to accompany the textbook:
%  Information and Computing Science: A Laboratory Course

i=zeros(n+2,1);
i(n+2)=a(n+1)/(n+1);
for k=n+1:-1:2
    i(k)=a(k-1)/(k-1)+i(k+1)*x;
end
i(1)=c+i(2)*x;
iy=i(1);