Well, I must express this trajectory: $\displaystyle \vec{r}=(t^2,2t,t^2)$ as an intersection of two surfaces. I really don't know how to work this. It seems to be some kind of parabola, I've tried to figure it out how it would look, and I get how it would look on the planes xy and xz, but I'd really like to see some step by step for solving this. I couldn't get anywhere yet.

Bye, and thanks off course.