Is this a function or relation? How can I tell?

http://static.k12.com/eli/bb/812/-1/0/2_36582_44214/-1/667c15a34913240ec807a3aeebd1c986ad065e37/media/fa08b1621709127b90b5480d6ab861ea3ab65963/mediaasset_670072_1.bmp

Question

Is this a function or relation? How can I tell? 

http://static.k12.com/eli/bb/812/-1/0/2_36582_44214/-1/667c15a34913240ec807a3aeebd1c986ad065e37/media/fa08b1621709127b90b5480d6ab861ea3ab65963/mediaasset_670072_1.bmp

nipunmalhotra93 · Answer

a function from A to B is a set of points (x,y) where every x in A is related to one and only one y in B.
a relation from A to B is a set of points (x,y) where every x in A is related to every other y in B.
you can see here that for every x, f(x) has only one value.
so, every x is mapped to a single y 
so it is a function

directrix · Answer

@elizabethann509
Check out the vertical line test for a function. For those of us who are visual learners, it is convenient. See attached file.

anonymous · Answer

@Directrix 

I would do the vertical/horizontal line tests but I don't understand how they work. I learned about them in class but I still don't understand.. I'm awful at math.

directrix · Answer

@elizabethann509   Are you online now?

directrix · Answer

@elizabethann509  Do you know the definition of a function - the part that talks about for every x, there is at most one y that is paired with that x?