3 -7 2 4-2 5 1 -3 2 -5 -1 2 4 -6 3 8r2+r33 -7 2 40 0 0 -12 -5 -1 24 -6 3 8按第2行展开D = -1 * (-1)^(2+4) *3 -7 22 -5 -14 -6 3r1+2r2,r3+3r2 7 -17 0 2 -5 -110 -21 0按第2行展开D = -1*(-1)*(-1)^(2+3)* 7 -1710 -21= -23