(1)x+2y+3z=11(1)x-y+4z=10(2)x+3y+2z=2(3)(1)-(2)得,3y-z=1,(4)(3)-(2)得,4y-2z=-8,即2y-z=-4,(5)(4)-(5),得y=5,代人得z=14,x=-39所以x=-39y=5,z=14(2)x:y=3:5(1)y:z=5:6(2)x+y+2z=40(3)由（1）得,x=(3/5)y,由（2）...