Please answer a & b

9. (14 points) Consider the surface z = x2 + y2. (a) (7 points) Write down a line that passes through the point (1, 1, 2) and is perpendicular to the tangent plane of the surface at that point. Answer: (b) (7 points) The curve r(t) = (t + 1, a(t2 + t) + 1, 2at + 2) touches the surface z = x2 + 2 at time t = 0. For which values of a is the curve r(t) tangent to the surface at t = 0