已知集合S的运算☆满足(1)x☆x=x (2)(x☆y)☆z=(y☆z)☆x,求证x☆y=y☆x (其中x,y∈S)
已知集合S的运算☆满足(1)x☆x=x (2)(x☆y)☆z=(y☆z)☆x,求证x☆y=y☆x (其中x,y∈S)
设整数n≥4,集合X={1,2,3,…,n}.令集合S={(x,y,z)|x,y,z∈X,且三条件x<y<z,y<z<x
设x.y.z满足3x=4y=6z(x.y.z都是指数)求证
x分之y+z=y分之z+x=z分之x+y(x+y+z不等于0),求x+y+z分之x+y-z
已知x/2=y/3=z/4,求下列各式 (1)(x+y+z)/x (2)(x-y+2x/(x-y-2z)
已知x::y:z=3:4:5,(1)求x+y分之z的值;(2)若x+y+z=6,求x,y,z.
已知X Y Z满足3x-2y+z的绝对值+2x+y+2z的绝对值=0(x,y,z不等于0),求x+y除以Z的值
已知X,Y,Z满足|3X-2Y+Z|+|2X+Y+2Z|=0(X,Y,Z≠0),求(X+Y)/Z的值
已知x+1/y=Y+1/Z=1,(1)求z+1/x的值 (2)如果实数x,y,z.满足x+1/y=4,y+1/z=1,z
已知实数x,y,z满足:x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,则x+y+z=
设Z=X+Y,其中X,Y满足X+2Y>=0,X-Y
已知x,y满足约束条件x−y+5≥0x+y≥0x≤3,则z=x+2y的最小值为( )