Question

what are 3 methods of identifying a function?

Answer 1

one is vertical line test

Answer 2

i think if it is equal to 0

Answer 3

thanks I need two more

Answer 4

yes, the vertical line test is to identify [an explicit] function.
So vertical line test is #1.

Perhaps you can just check if any x-coordinate repeats twice (if you for example have a table of x and y values).

Answer 5

If checking this, wouldn't be considred the exact same thing as the vertical line test.....