Question

解方程{x+2y=5 x-y+2z=1 2x+y-z=3

Answer 1

x+2y=5 -----(1)

x-y+2z=1 -----(2)

2x+y-z=3 -----(3)

由(1)式可得x=5-2y,代入(2)(3)式：

5-3y+2z=1,即3y-2z=4 ------(4)

10-3y-z=3,即3y+z=7 ------(5)

(5)-(4)可得：3z=3,即：z=1

代入(5)得：y=2

代入(1)得：x=1

所以,方程组的解是：x=1,y=2,z=1