Bézier curve for some nodes

Question

How do I write the Bézier curve with the nodes $(x_1,y_1),(x_2,y_2)$and control points $(x_3,y_3),(x_4,y_4)$? I know how to write it as parametric form with $x(t)$ and $y(t)$, but I have no idea how to write it directly