The null() function gives you a basis for ker(A):
A=[0.719600000000000,0.069400000000000,0.526400000000000,0.110700000000000;1.833200000000000,0.377900000000000,1.469000000000000,0.454700000000000];
N = null(A)
A*N
So every linear combination of these two vectors will give a vector n with A*n = 0.
"lsqlin" could be used instead if you want to set lower and upper bounds in the coordinates of n. But note that it might happen that no solution exists.
The following code solves for a vector with positive first component n1:
C=[0.719600000000000,0.069400000000000,0.526400000000000,0.110700000000000;1.833200000000000,0.377900000000000,1.469000000000000,0.454700000000000];
d=[0;0];
Aeq = [1 0 0 0];
beq = 1;
n = lsqlin(C,d,[],[],Aeq,beq)
C*n
