Question: A student was asked to find the equation of the tangent plane to the surface z = x3 - y2 at the point (x, y) = (2, 3). The student's answer was
z = 3x2 (x - 2) - 2y(y - 3) - 1.
(a) At a glance, how do you know this is wrong?
(b) What mistake did the student make?
(c) Answer the question correctly.