A=[-21,19,-20; 19,-21,20; 40,-40,-40];
B=[0; 1; 2]; C=[1,0,2]; D=0; G=ss(A,B,C,D);
[y,t,x]=step(G);
Y=-G.c*inv(G.a)*G.b+G.d

dc=dcgain(G) %direct call of function 

plot(t,y), figure, plot(t,x)