As we saw in Figure 3.5

, one way to show convexity of indifference curves is to show that for any two points 1x1, y12 and 1x2, y22 on an indifference curve that promises U 5 k, the utility associated with the point a x1 1 x2 2 , y1 1 y2 2 b is at least as great as k. Use this approach to discuss the convexity of the indifference curves for the following three functions. Be sure to graph your results.

a. U 1x, y2 5 min 1x, y2.

b. U 1x, y2 5 max 1x, y2.

c. U 1x, y2 5 x 1 y.