设A=第一行[ 1 -2 3k] 第二行[-1 2k -3]第三行[k -2 3],问k何值时,可使（1）R(A)=1；（2）R(A)=2;(3)R(A)=3

r2+r1,r3-kr1
1 -2 3k
0 2k-2 3k-3
0 2k-2 -3k^2+3
r3-r2
1 -2 3k
0 2(k-1) 3(k-1)
0 0 -3(k-1)(k+2)
k!=1且 k!=-2时,r(A) = 3;
k = -2 时,r(A) = 2.
k = 1 时,r(A) = 1