Oh yeah, and don't just write down "-2", it's meaningless on its
own. Specify *what* equals -2 (yeah I know, in this case it's
clearly y) because then you have to go and get what x is and
that will probably be something completely different.  Like
saying "How old are Fred and Mary?" You know Fred's 12 but you
don't know Mary's age, so you say, "12." No you don't, you say
"Fred's 12."