Different equation of all parabola with x axis as the axis and $(a,0)$ as the focus

Question

$(a)\;y \frac{dy}{dx} =2a \\ (b)\;\bigg(\frac{dy}{dx}\bigg)^3+\bigg(\frac{dy}{dx}\bigg)^2 (2x-2 \theta)+y=0 \\ (c)\;\bigg(\frac{dy}{dx}\bigg)= \frac{y}{2} \\ (d)\; \frac{dy}{dx}+(x-a)y=2 $