x(1/y+1/z)+y(1/x+1/z)+z(1/x+1/y)+3=x/y+x/z+y/x+y/z+z/x+z/y+3=(x/y+1+z/y)+(x/z+y/z+1)+(1+y/x+y/x)=(x+y+z)/y+(x+y+z)/z+(x+y+z)/x=(x+y+z)(1/x+1/y+1/z)已知x(1/y+1/z)+y(1/x+1/z)+z(1/x+1/y)+3=0 且1/x+1/y+1/z≠0那么(x+y+z)(1/x+1/y+1/z)=0即(x+y+z)=0 为解