Q.

The greatest integer function f:R→R, given by f(x)=[x] is:

1 one-one  
2 onto  
3 both one-one and onto  
4 neither one-one nor onto  

Ans.

(4)

Ans.      neither one-one nor onto

Explanation:

We know

                            [2.2] = 2

                            [2.5] = 2

∵                       [2.2] = [2.5]

but                         2.2 ≠ 2.5

⇒f is not one-one function.

Now, consider 0.6∈R

It is known that f(x)=[x] is always an integer. Thus, there does not exist any element x∈R such that f(x)=0.6.

∴   f is not onto.

Hence, greatest integer function is neither one-one nor onto.