x+y=12 y+z=20 z+x=18 求X Y Z分别等于几?

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x+y=12 y+z=20 z+x=18 求X Y Z分别等于几?
x+y=12 y+z=20 z+x=18 求X Y Z分别等于几?

x+y=12 y+z=20 z+x=18 求X Y Z分别等于几?
x+y=12
y+z=20 z-x=8
z+x=18
2z=26
z=13
y=7
x=5

x+y=12 (1)
y+z=20 (2)
z+x=18 (3)
(1)+(2)+(3)
2(x+y+z)=50
x+y+z=25 (4)
(4)-(2)，x=5
(4)-(3)，y=7
(4)-(1)，z=13

x=5，y=7，z=13

x+y=12 (1)
y+z=20 (2)
z+x=18 (3)
[(1)+(2)+(3)]/2
x+y+z=25 (4)
(4)-(2) x=5
(4)-(3) y=7
(4)-(1) z=13

解方程 x(x+y+z)=6 y(x+y+z)=12 z(x+y+z)=18 解方程组{x(x+y+z)=6,y(x+y+z)=12,z(x+y+z)=18 (x+y-z)(x-y+z)= x+y=12 y+z=20 z+x=18 求X Y Z分别等于几? X+Y+Z=? x/y=(x+z)/(y+z)y/z=(x+y)/(x+z) 已知 x/(y+z)+y/(z+x)+z/(x+y)=1求 (x*x)/(y+z)+(y*y)/(x+z)+(z*z)/(x+y)=? (y+z)/x=(z+x)/y=(x+y)/z求x+y-z/x+y+z的值 x-4y+z=-302x+y-z=18x--y-z=7 x+y=8 y+z=12 x+z=10 x+y+z= x+y=8 y+z=12 x+z=10 x+y+z= X+Y+Z=26X-Y=12X-Y+Z=18 fangchengzu:X+Z=Y 7Z=X+Y+Z X+Y+Z=14 z+=x>y?++x: 方程组 (1) x+2y-3z=12 x-3y+2z= - 13 x-y-z=0 (2) x+ y=z 5x-y+z=18 2x+5y+3z= -1 用行列式的性质证明：y+z z+x x+y x y z x+y y+z z+x =2 z x y z+x x+y y+z y z x 这个怎么证? x=y; y=z; z=x/y x+y+z=12 x-y+z=2 x-z+y+a=90 x+y+a+z=100,求x y z a