1.{5x=7y-1 5x=17-14y 2.{x=16-4y y=34-4x 3.{x+y=7 x:5=y:2 4.{x+2y=1 x-4y=-22 5.{3x=y+1⼀2 3x=y⼀4

1. 5x=7y-1 ----(1)
5x=17-14y ----(2)
(1)*2+(2), 15x=15, x=1.
5=7y-1, y=6/7.

2. x=16-4y ----(1)
y=34-4x ----(2)
(1)代入（2） y=34-4(16-4y), y=34-64+16y, y=2
x=16-8=8.

3. x+y=7 ----(1)
x:5=y:2 ----(2)
由(1)得 y=7-x, 代入(2)得 x:5=(7-x):2,
2x=35-5x, 7x=35, x=5;
y=7-x=2.

4. x+2y=1----(1)
x-4y=-22----(2)
(1)-(2), 6y=23, y=23/6
x=1-2y=-20/3

5. 3x=y+1/2 ----(1)
3x=y/4----(2)
(1)-(2), 3y/4+1/2=0, y=-2/3
3x=y/4=-1/6, x=-1/18.

1.X=1 Y=6/7
2.X=8 Y=2
3.X=5 Y=2
4X=0 Y=1/2
5X=-1/6 Y=-2/3