x+y+z=142 x/28+y/30+z/35=4.5 z/28+y/30+x/35=4.7 怎么解.

(x+y-z)(x-y+z)= 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/30+y/28+z/35=4.5 x/30+y/35+z/28=4.7 x+y+z=142 这个方程怎么解?详细过程 x+y+z=142 x/28+y/30+z/35=4.5 z/28+y/30+x/35=4.7 怎么解. 一道三元一次方程六年级的速度!x/28+y/35+z/30=4.5 ｛x/35+y/28+z/30=4.7 x+y+z=142 解方程组：x/28+y/35+z/30=4.5①；x/35+y/28+z/30②；x+y+z=142③ (y+z)/x=(z+x)/y=(x+y)/z求x+y-z/x+y+z的值 z+=x>y?++x: x=y; y=z; z=x/y 6x+5y+3z=100 x+y+z=30 求 x y 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+z=28 x+y=16 y+z=14,求x、y、z分别是什么数? x/(y+z+u)=y/(z+u+x)=z/(u+y+x)=u(x+y+z)求(x+y)/(z+u)+(y+z)/(y+x)+(z+y)/(x+y)+(u+x)/(z+y) 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z fangchengzu:X+Z=Y 7Z=X+Y+Z X+Y+Z=14 若z分之x+y+z=y分之x-y+z=x分之-x+y+z,求xyz分之(x+y)(y+z)(z+x)