What difference is there please tell me in a mathematical way​

In The first diagram, we know that its a function because each element of x has a unique face in y. That is, each element in x is joined with exactly one unique element in y. If an element from x is connected to 2 faces in y, i.e, 1 element in y connected to 2 elements in x, then it's not a function. this is what has happened in figure 2, where 1 is connected to -0 and 15.

Regards,

Astrix <3

answer by yourhope:

hi! : )

a farmer that lived in ancient egypt would most likely be barried in the sand, in the desert!

: )