作业帮x+y+z=12 x-y+z=2 x-z+y+a=90 x+y+a+z=100,求x y z a
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x+y+z=12 x-y+z=2 x-z+y+a=90 x+y+a+z=100,求x y z a
x+y+z=12 x-y+z=2 x-z+y+a=90 x+y+a+z=100,求x y z a
x+y+z=12 x-y+z=2 x-z+y+a=90 x+y+a+z=100,求x y z a
x+y+z=12① x-y+z=2② x-z+y+a=90③ x+y+a+z=100④
①+②得2x+2z=14 x+z=7⑤
②+④得2x+2z+a=102⑥
⑥-⑤*2得a=88⑦
②+③得2x+a=92⑧
把⑦代入⑧中得2x=4 x=2⑨
把⑨代入⑤中得z=5⑩
把⑨⑩代入①得y=5
∴x=2,y=5,z=5,a=88
(打得好累哦)
x+y+z=12 x-y+z=2 可求得 y=5
x-z+y+a=90 x+y+a+z=100 可求得 z=5
由y=5 z=5 可知 x=2 a=88
分别记为1、2、3、4式，则
1式减2式得：2y=10，所以y=5；
4式减3式得：2z=10，所以z=5；
把y=5、z=5代入1式得x=2；
代入3式得a=88
经检验，无误，即a=88、x=2、y=5、z=5
a=88,x=2,y=z=5
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