Df = R. Let a be any real number. Three cases axis : Case I: a > 1 In this case, all nearby points of a are also .> 1
⇒ f is continuous for all a > 1 Case II : a < 1 In this case, all nearby points of a are also < 1 ⇒ f is continuous for all a < 1. Case III : a = 1 ∴ nearby points can be either <1 or > 1. ⇒ f is continuous at x = 1 ∴ f is continuous at every point of its domain.