f(x) = x2 - 2ax + a (a + 1) Let y = f(x) = (x−a)2 + a , x ∊ [a , ∞) Clearly y ≥ a (x−a)2 = y - a x = a + √y−a f−1 (x) = a + √x−a (x−a)2 + a = a + √x−a ∵ f(x) = f−1 (x) ⇒ x = a (or) (x−a)3 = 1 ⇒ x = a (or) a + 1 If a = 5049 , then a + 1 = 5050 If a + 1 = 5049 , then a = 5048