!) Define the functions: 906,3!) = (x 1)2 + (y - 1)2 Way) = -(x - 2)2 - (y - 2)2 ROW) = x2 -;V2 a) For each function, find all the points which have a tangent plane parallel to the xyplane. Tha is, find where there are horizontal tangent planes. b) For an appropriate function f, discussed at a later point in the course, we will define 2 D = 001,19) = fxxC-a, b)fyy(a, b) - [fxy(a, b)] Compute D for all the points found in part a). In a table, list each point along with its corresponding value for D and fxxCa, b). c) By examining the graphs ofthese functions (e.g. in Geogebra). Comment about the points yOI found in part a) and their corresponding values in your table. Hint: think about increasing/decreasing/extrema