can you prove?

Let f : R" > R be a function. (6.1) f is a one-toone (injective) function if for every :1: E R\" and y E R" such that 3: 7E y, we have f (:8) 7E f (y) Prove the following proposition: If f is a onetoone function, then a( f ) is a convex set for each 04 E R