# Which of the following is true? A function f : X → Y is invertible if and only if:

a) f is one-one, b) f is onto, c) f is one-one and onto, d) f is neither one-one nor onto.

Answer: c) f is one-one and onto.

# A function f : X → Y is invertible if and only if f is one-one and  onto.

edited Jun 12, 2013