A-level maths help!

Hello, I have no idea where to even start with part c of this question. I have gotten the rest right its just part c I am really confused on.

How could you find an expression for the velocity?

I attached a photo.

You need dy/dx

I still do not get it. Why do you need dy/dx?

I still do not get it. Why do you need dy/dx?

If your position vector at any time is r = xi + yj then the velocity vector at that time is v = dr/dt. One component will be (dx/dt)i, but the other component (the j-part) requires dy/dt and hence the chain rule so that you can also express it in terms of dx/dt.

They have an expression in part (a) for y in terms of x.

Yes - I was reinforcing your point that they're going to need dy/dx as part of the calc. Or have I missed something?