If x,y,z are three real numbers of the same sign, then the value of (xy+yz+zx) lies in the interval
If x, y, z are three real numbers of the same sign then the value of x/y +y/z+z/x lies in the interval
If (x2+y2+z2)=(xy+yz+zx), what is the value of x3+y3+z3?