Answer:
Number one is only a function
Explanation:
A function has all different x values, but if there are two of the same x values with different y values, that is not a function. It’s okay if there are two do the same x values- they just have to have the same y values.
Number one has all different x values
Number two has an x value with two different y values, therefore it is not a function
Number 3 has two of the same x values but with different y values, so it’s not a function
Number four is not a function because of the vertical line test. You pick a point on the line and draw a vertical line all the way through the line. If that point passes through any other points, that it is not a function. Number four doesn’t pass the vertical line test, so it’s not a function.