Question

解方程组（要步骤）

{x＋y=7
{y+z=3
{z+x-2=0

Answer 1

{x＋y=7 (1)
{y+z=3 (2)
{z+x-2=0 (3)
(1)-(2)得x-z=4 (4)
(3)+(4)得
x=3
代入（1）得y=4
代入（3）得z=-1

Answer 2

x=7-y
z=3-y
代入z+x-2=0
即3-y+7-y-2=0
y=4
x=3
z=-1

Answer 3

y=7-x
y=3-z
7-x=3-z和z+x-2=0联立解
得z=-1 x=3
y=4

Answer 4

{x+y=7}&{y+z=3}=>{x-z=4}
{x-z=4}&{z+x-2=0}=>2x=6 =>x=3 =>z=-1 =>y=4

Answer 5

x=7-y
z=3-y
3-y+7-y-2=0
y=4 x=7-4=3 z=3-4=-1