Answer:
The given statement is false.
Explanation:
One-One function
A one-one function is a function such that for every value in domain there is exactly one point in domain.
Or in other words it can be written as:

The absolute value function is not one-one.
This can be explained with the help of an example:


Thus, for two values in co-domain it have same values in range.
The greatest integer function is not one-one. This can be shown with the help of a counter example:
![f(x) = [x]](https://img.qammunity.org/2017/formulas/mathematics/high-school/jkd3l4okm8qk5jeopbo2z6r1jxd5sz0b62.png)

Since for multiple values in domain, we have the same value in range, there greatest integer function is not one-one.