X-2Y =-9 Y-Z =3 2Z+X=47 方程解

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X-2Y =-9 Y-Z =3 2Z+X=47 方程解
X-2Y =-9 Y-Z =3 2Z+X=47 方程解

X-2Y =-9 Y-Z =3 2Z+X=47 方程解
①X-2Y =-9
②Y-Z =3
③2Z+X=47
由②得Y＝3+Z,代入①得④式：X－2Z＝－3
③+④得：2X＝44,X＝22
X代入③得：2Z＝25,Z＝12.5
由②得Y＝3+Z＝15.5
X＝22、Y＝15.5,Z＝12.5

x=2y-9, z=y-3,2z+x=2y-6+2y-9=47,y=31/2,x=22,z=25/2

X-2Y =-9 (1)
Y-Z =3 (2)
2Z+X=47 (3)
由(2)*2+（3）得
x+2y=53 (4)
(1)+(4)得
2x=44 x=22 代入(1) 得y=31/2 代入(2)得 z=25/2

z=y-3代入2z+x=47得2y+x=53,此式和X-2Y =-9相加得2x=44,x=22.再代入X-2Y =-9得y=15.5,所以z=12.5

(1)-(3) : -2y-2z=-56
y+z=28 (4)
(2)+(4): 2y=31
y=15.5
z=12.5
x=22

1. y=z+3
2.（y=z+3）代入其1式中
3. 得 x-2(z+3)=-9；2z+x=47
4.得x-2z=-3；2z+x=47
5.得x=22；z=25/2；y=31/2

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