作业帮x+y+z=0,3x-2y-2z=5,y-z=2x-7
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x+y+z=0,3x-2y-2z=5,y-z=2x-7
x+y+z=0,3x-2y-2z=5,y-z=2x-7
x+y+z=0,3x-2y-2z=5,y-z=2x-7
3个式子分别标号（1）（2）（3）
（1）X2：2x+2y+2z=0;
(1)x2 +(2):5x=5; x=1;
x=1带入（3）中得 y-z=-5; 此式称为（4）;
x=1带入（1）中得 1+y+z=0 变换一下 y+z=-1；此式称为（5）；
（4）+（5）得 2y=-6 ; y=-3;
y=-3带入 （4）或（5）中 得 z=2;
综上述 x=1 y=-3 z=2
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