Question

Which of the following represents a function?

Answer 1

See explanation below

Explanation:

A function is an aplication from a set A to other B such that, very element from A has a unique "associated" element by function.

In first case: There is an element (3), with 2 arrows, so this element has no unique element in y. Is not a function

Second case: there are 2 pairs (-1,-11) and (-1,-5) saying that element -1 has 2 associates by function. Is not a funtion

Third case: again, 3 has two elements associated by function (14 and 19). Is not a function

Last case: Is a function because every element in x-axis has an only element associated by aplication. The functional relationship is a quadratic relationship. (Parabola)

Hope this helps