a. 0.1120.1120.112 b. fprom≈0,175f_{prom}\approx 0,175fprom≈0,175; aquí f(0.4,0.2)≈0.1,f(0.2,0.6)≈−0.2,f(0.8,0.2)≈0.6f (0.4,0.2) \approx 0.1, f (0.2,0.6) \approx − 0.2, f (0.8,0.2) \approx 0.6f(0.4,0.2)≈0.1,f(0.2,0.6)≈−0.2,f(0.8,0.2)≈0.6, y F(0.8,0.6)≈0.2F (0.8,0.6) \approx 0.2F(0.8,0.6)≈0.2.