Given equation:
1+(dxdy)2=[adx2d2y]21
The order of a differential equation is determined by the highest derivative present in the equation.
Examining the equation, the derivatives present are:
dxdy (first derivative)
dx2d2y (second derivative)
The highest derivative in the equation is the second derivative dx2d2y.
The square roots and powers do not affect the order. Order only depends on the highest derivative present.
Therefore, the order of the differential equation is 2.