How to find response

Hello, I put the following system in matlab but I get an error

"When simulating the response to a specific input signal, the input data U must be a matrix with as many rows as samples in the time vector T, and as many columns as input channels."

Can someone explain it to me? Thank you.

A = [3 0;0 -2];
B = [3 0;0 -2];
C = [-1 1;1 -1];
D=0;
x0 = [1 -1]; 
poles = eig(A) 
% open-loop response:
t = 0:0.01:5;
u = 0*t;
sys = ss(A,B,C,D);
[y,t,x] = lsim(sys,u,t,x0);
plot(t,y)

Answer 1

[Azzi Abdelmalek]

A = [3 0;0 -2];
B = [3 0;0 -2];
C = [-1 1;1 -1];
D=0;
x0 = [1 -1]; 
poles = eig(A)  % You have unstable poles (pole=3)
% open-loop response:
t = (0:0.01:5)';
u = [sin(t) sin(t)]  % create your input signals
sys = ss(A,B,C,D);
[y,t,x] = lsim(sys,u,t,x0);
plot(t,y)