let f(x,y) = 4x^2 - 6x^2 (sqrt(y)) and let γ(t) = <x(t),y(t)> be a curve in the Oxy plane such that at some point t0, we have γ(t0) = (-1,9) and γ'(t0) = (2,-1). Find the tangent vector r'(t0) to the curve r(t) = <x(t),y(t), f(x(t), y(t))> at the point t0.
