r1-2r4,r2-r40 8 9 -110 9 7 -120 -5 -1 21 0 -7 6按第1列展开,D = 1*(-1)^(4+1)* 8 9 -11 9 7 -12-5 -1 2c1-5c2,c3+2c2-37 9 7-26 7 2 0 -1 0按第3行展开D = -(-1)*(-1)^(3+2)*-37 7-26 2= -(-37*2+7*26)= -108.