1 2 3 4 1 -2 4 5 1 10 1 2 r2-r1,r3-r1 1 2 3 4 0 -4 1 1 0 8 -2 -2 r3+2r2 1 2 3 4 0 -4 1 1 0 0 0 0 所以 r(A)=2.
