[(dx2d2y)2−3]1/3=2(dxdy)1/4.
To make all derivative powers integer, raise both sides to the 12th power. Equivalently, the LHS becomes [(dx2d2y)2−3]4 and the RHS becomes 212(dxdy)3.
Highest derivative is dx2d2y, so order =2. Highest power of this derivative after rationalisation is 2×4=8, so degree =8.