What is the degree of the differential equation $${{{d^3}y} \over {d{x^3}}} + {\left( {{{dy} \over {dx}}} \right)^2} - {x^2}\left( {{{{d^4}y} \over {d{x^4}}}} \right) = 0$$ ?

Which one of the following is the differential equation that represents the family of curves $$y = {1 \over {2{x^2} - C}}$$,where C is an arbitrary constant?

The differential equation which represents the family of curves given by $$\tan y = C(1 - {e^x})$$ is

The solution of the differential equation $${{dy} \over {dx}} = \cos (y - x) + 1$$ is