(a)
Given differential equation is
$y = x\ \frac{dy}{dx} + \left( a^{2}\left( \frac{dy}{dx} \right)^{2} + b^{2} \right)^{\frac{1}{3}}$
$\Rightarrow$ $\left( y - x\ \frac{dy}{dx} \right)^{3} = a^{2}\left( \frac{dy}{dx} \right)^{2} + b^{2}$
$\therefore$ Order and degree of the above differential equations are 1 and 3 respectively.