x1=rand(1,11);x2=rand(1,11);n=0:10;
alpha=2;beta=3;
k=0:500;
w=(pi/500)*k;
X1=x1*(exp(-j*pi/500)).^(n'*k);
X2=x2*(exp(-j*pi/500)).^(n'*k);
x=alpha*x1+beta*x2
X=x*(exp(-j*pi/500)).^(n'*k);
X_check=alpha*X1+beta*X2
error=max(abs(X-X_check))