1. The problem statement, all variables and given/known data A particle is moving along the graph of y=sqrt(x). At what point on the curve are the x-coordinate and the y-coordinate of the particle changing at the same rate? 2. Relevant equations y = sqrt(x) y' = 1/(2sqrt(x)) 3. The attempt at a solution The solution to the problem is to differentiate both sides of the eqn with respect to time and then determine when dy/dt = dx/dt. But I don't understand how the x-coordinate has a rate of change since it's an independent variable? Can someone explain how to comprehensively understand the solution and I suppose, wording of this problem? Thank-you.