The equation of the curve passing through the point ($$-$$1, $$-$$2), which satisfies $${{dy} \over {dx}} = - {x^2} - {1 \over {{x^3}}}$$ is

What is the order of the differential equation whose solution is $$y = a\cos x + b\sin x + c{e^{ - x}} + d$$, where a, b, c and d are arbitrary constants?

What is the solution of the differential equation $$\ln \left( {{{dy} \over {dx}}} \right) = ax + by$$?

What is the solution of the differential equation $${{dx} \over {dy}} = {{x + y + 1} \over {x + y - 1}}$$ ?

Where, C is an arbitrary constant.