(9x)^2/3+(2y)^2/3+z^2/3
$$\\(9x)^2/3+(2y)^2/3+z^2/3\\\\ =(9*9*x^2)/3\quad +\quad(2*2y^2)/3\quad +\quad z^2/3\\\\ =\frac{81x^2+4y^2+z^2}{3}$$