Question

The function f :[2, ∞) → (0, ∞)  defined by f(x) = x² – 4x + a, then the set of values of ‘a’ for which f(x) becomes onto is 

(a) (4,∞) 

(b) [4,∞) 

(c) {4} 

(d) ϕ

Answer 1

Correct option (d)

Explanation:

f(x) = x² – 4x + a always attains its minimum value.

So its range must be closed.

So, a = {ϕ}