Assume that a point moves in (x,y) plane according to the above parametric equations. Find for which $t$ the velocity is equal to 9.
I have an idea about this problem, but I'm not sure how to work with it. If we are given the position functions, then the derivative is the velocity. The derivative of both of those with respect to t is $x=2t, y=9$, but I'm not sure what to do after that.