(a^2 + b^2 + 1) - (a + b + ab)= a^2 + b^2 - ab - a - b + 1= (1/2) (2a^2 + 2b^2 - 2ab - 2a - 2b + 2)= (1/2) [(a^2 - 2a + 1) + (b^2 - 2b + 1) + (a^2 - 2ab + b^2)]= (1/2) [(a-1)^2 + (b-1)^2 + (a-b)^2] >=...