The function is defined as
a. A mapping f : X ⟶ Y is said to be a function if each element in the set X has its image in set Y.
It is also possible that there are few elements in set Y which are not the images of any element in set X.
b. It is impossible to have more than one image for a specific element in set X. Functions can not be multi-valued.
1. In the graph given , the coordinates are given where each element of x has its image in y.
Hence it is a function.
2. The expression is given
In the given set , the element X has multi -values . Then it is not defined as a function.
3. The graph is given, and for the graph the coordinates are given where each element of x has its image in y.
Then it is defined as function.