1. The problem statement, all variables and given/known data The question is : Find the maximum and minimum lengths of the radius vector contained in an ellipse [tex]5x^2 +6xy+5y^2[/tex] 2. Relevant equations 3. The attempt at a solution Hi I seem to be at a loss here because usually along with an equation a constraint is also given but in this case there is just an equation or I maybe waffling along since I missed the lecture. Anyhow.. can anyone guide on how to solve this one ? [tex]\nabla f = \lambda\nabla g[/tex] Usually questions have a constraint which makes life much easier.. then however doesn't seem to have one :/ Or maybe the above equation is the constraint.. and the actual f(x,y) would be the equation of an ellipse ?