{x+y=7,y+z=8,z+x=13

(x+y-z)(x-y+z)= fangchengzu:X+Z=Y 7Z=X+Y+Z X+Y+Z=14 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)=? {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 (y+z)/x=(z+x)/y=(x+y)/z求x+y-z/x+y+z的值 x+y-z=3 y+z-x=5 z+x-y=7 求x,y,z 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-4y+z=-302x+y-z=18x--y-z=7 x+y+z=14 7z=x+y+2 x+z=y (x*x+2)(y*y+4)(z*z+8)=64xyz,求x,y,z 解方程x+y=7 y+z=8 z+x=13 {x+y=7,y+z=8,z+x=13 z+=x>y?++x: x+Y+Z=1 X+3Y+7Z=-1 X+5Y+8Z=2x+Y+Z=1X+3Y+7Z=-1X+5Y+8Z=2 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?