Question

解三元一次方程 {x+y+z=35 {2x-y=5 {1/3y=1/2z？

Answer 1

x+y+z=35-----------(1) ,2x-y=5-----------(2),1/3y=1/2z----------(3), 2z=3y

2x+2y+2z=70-----(1)     , (1)-(2)得：3y+2z=65, 6y=65, y=65/6,  z=65/4

2x=5+y=5+65/6=95/6, x=95/12,     

Answer 2

Z=2/3y,化为二元一次方程，x+5/3y=35,y=2x-5,化为一元一次方程，x+5/3*(2x-5)=35，x=10,y=15,z=10

Answer 3

将式子2：2x-y=5化简得x=(5+y)/2
将式子3：1/3y=1/2z化简得z=3y/2
都带入式子1，化简可以得到，5+y+2y+3y=70,
y=65/6,
x=95/12
z=65/4.

Answer 4

x+y+z=35(1)
2x-y=5(2)
1/3y=1/2z(3)
(1)x2-(2)得:
3y+z=65
z=65-3y(4)
(4)代入(3)得:
1/3y=1/2(65-3y)
(1/3+3/2)y=65/2
y=195/11
z=520/11
x=125/11

Answer 5