{(3,2) (4,9) (3,-4) (2,9)}

Question

Is this a function?

Answer 1

No, not a function

because there are 2 values of y for 1 value of x

(3,2) and (3,-4)

if you plot them, one is directly above the other.

by the vertical line test if you can draw a vertical line that intersects the graph in more than one point, then it's not a function.