1.3(x+y)-4(x-y)=4 x+y/2 + x-y/6 =6 2.x+2y+3z=7 2x+y+z=7 3x+y+2z=11 3.x:y:z=1:2:7 2x-y+3z=21
问题描述：
1.3(x+y)-4(x-y)=4 x+y/2 + x-y/6 =6 2.x+2y+3z=7 2x+y+z=7 3x+y+2z=11 3.x:y:z=1:2:7 2x-y+3z=21
4.4x-3y=1 x+2y-z=5 3x-y+2z=2
答
1:1.3(x+y)-4(x-y)=4,(1)x+y/2 + x-y/6 =1 (2)由(1),得:x=7y-4,代入(2),得14y-y/3=9,y=27/41,x=25/412.5x+4y+z=0,(1)3x+y-4z=11,(2) x+y+z=-2 (3)4(1)+(2):23x+17y=11 (4)(1)-(3):4x+3y=2 (5)3(4)-17(5):x=-1由(5),y...