Q. Find the maximum and minimum distance of a point from origin such that the point lies in the curve $3x^2+4xy+6y^2=140$
I am unable to solve these three equations simultaneously for $(x,y)$
$2x+\lambda(6x+4y)=0$
$2y+\lambda(4x+12y)=0$
$3x^2+4xy+6y^2=140$