1. The problem statement, all variables and given/known data Find a parameterization for the motion described by x = -3z^2 in the xz plane. 2. Relevant equations 3. The attempt at a solution For circles and stuff, I get the general process, but for these simple ones, they feel a little too easy. Is it valid for me to say: let x(t) = t then z(t) = -3t^2 and y(t) = 0 because of it's location in the plane constantly of xz. Can I always just solve the equations for one side and define it to be equal to t, adjusting the remaining equation(s) accordingly?