A=[0,1,0,0; 0,5,0,0; 0,0,-7,0; 0,0,0,-8];
B=[0; 1; 0; 1]; C=[1,2,3,4]; D=0;
p=eig(A)'

p1=p; p1(1:2)=[-1,-2]; K1=place(A,B,p1)

eig(A-B*K1)'

p2=p; p1(1:3)=[-1,-2,-3]; K2=place(A,B,p2)

eig(A-B*K2)'

[Ab,Bb,Cb]=ctrbf(A,B,C); Ab, Bb