Which equation is a function of x

Question

X=5

x=y2+9

x2=y

x2=y2+16

Answer 1

Definition of a Function. A function is a relation for which each value from the set the first components of the ordered pairs is associated with exactly one value from the set of second components of the ordered pair.

This means that each x can have only one y. But, a y can have more than one x.

X=5 This is a straight vertical line running through x = 5. It has infinite y values and is not a function therefore.

Etc.