( a ) One - one into (b) Many-one into

Example Which of the following graph of y = f ( x ), represent functions and which does not ? Give reasons for your answers.

Solution :

1. No, for every x there are two images.

2. Yes, it is a function.

3. No, there are four images for same x

4. No, there are two values of y for x = 0

5. Yes, a function ( known as step function )

6. No, there are many images for some x

7. No, there are two images for some x.