jianyan.m

signal and system answer

%依托que1cdniheright
x=1:1:40;
y=-0.03.*x.*x+1.6.*x+18;
y1=mean(cdnihemean);
z=0;x=0;
for i=1:40
    z=z+(y(i)-y1)*(y(i)-y1);
end
for i=1:40
    x=x+(y(i)-cdnihemean(i))*(y(i)-cdnihemean(i));
end
f=z*38/x;