(a) Let f(x, y) = x²+y². Estimate f_x(2, 1) and f_y(2, 1) using the contour diagram for f in Figure 8.52.
(b) Estimate f_x(2, 1) and f_y(2, 1) from a table of valuesfor f with x = 1.9, 2, 2.1 and y = 0.9, 1, 1.1.
(c) Compare your estimates in parts (a) and (b) with the exact values of f_x(2, 1) and f_y(2, 1) found algebraically.

3 2 1 -1 -2 -3 % -3 -2 -1 y 1 2 3 Figure 8.52 X