( )—( )=9 + +( )—( )=14 || || 12 2设:x-y=9,z-w=14,x +z=12,y +w=2则:x-y=9(1)x+z=12(2)z-w=14(3)y+w=2(4)(4)+(3):z-w+y+w=2+14y+z=16(5)(2)-(1): x+z-x+y=12-9y+z=3(6)(5)(6)矛盾因此:原方程组无解。即:此题无解