Is { (1,-2), (-2,0), (-1,2), (1,3) } a function

Step-by-step explanation:

No ... this is not a function.

A function will not have ANY repeating x values ... they can have repeating y values, just not the x ones.

And this set of numbers has repeating x values of 1

in other words, in a function, all the x values have to be different numbers ... none can be the same