A bit of a tough one! Find the maximum of [tex]ln x + ln y + 3 ln z[/tex] on part of the sphere [tex]x^2 + y^2 + z^2 = 5r^2[/tex] where x>0, y>0 and z>0. I know I need to use Lagrange multipliers but how should I go about it? Any help would be appreciated thanks!!!