Let's begin by listing out the given information:
I.
![(x,y)=(1,3),(2,5),(3,4),(4,7)](https://img.qammunity.org/2023/formulas/mathematics/college/vw1pbo2i6c61bjjwz8yfwndxtedmzgs70x.png)
II.
![(x,y)=(1,3),(1,5),(2,4),(3,7)](https://img.qammunity.org/2023/formulas/mathematics/college/mnk490oicmjnv2u2rx39w3ls2hm2aiolli.png)
A function assigns one element of x in a set A to exactly one element called f(x) in a set B
The first function
Every element of x has a distinct element in y.
the second function
The element x = 1, has 2 different elements in y. We see y has 2 different values from the same value of x
Therefore, the first function defines y as a function of x