若A,B,C能构成三角形,则AB,AC,BC相互不平行AB=6I-3J-3I+4J=3I+JAC=-3I+4J+(5-M)I-(4+M)J=(2-M)I-MJBC=-6I+3J+(5-M)I-(4+M)J=(-1-M)I+(-1-M)J即(2-m)/3≠(-m)/1 解得M≠- 1(-1-M)/3≠(-1-M)/1 解得M≠- 1(-1-M)/(2-m)...