Answer:
1 and 2 is a function.But the third one isn't.
explanation:
When there is more than one point on a vertical line that is not a function.Like in the third picture points (2,1) and (2,-1) are on the same vertical line.
P.S: it is a function if there is more than one point on a horizontal line.
Why you may ask:
x are the domain, y are the codomain. X can have multiple Y but Y can't have more than one X. To embody: think Xs as mothers and Ys as childrens , a mother can have more than one children but every children can have only one biological mother.
