Question

Which relation is a function?
http://static.k12.com/calms_media/media/1417000_1417500/1417250/1/5777f7f0552e79387010b19944ad5ad6382e1309/MS_PA_130905_170056.jpg
http://static.k12.com/calms_media/media/1417000_1417500/1417251/1/6b2bdac1e2fa3c7b9c55470a43d119d61df2b5e9/MS_PA_130905_170057.jpg
http://static.k12.com/calms_media/media/1417000_1417500/1417252/1/89867371590aef555fd347857ff82efabb475a92/MS_PA_130905_170058.jpg
http://static.k12.com/calms_media/media/1417000_1417500/1417253/1/b34d9ef463e10ac51765581222931bb6f3b55e01/MS_PA_130905_170059.jpg

Answer 1

Its A B C D going down from top to bottom. Sorry i couldnt figure and other way to get the pic's

Answer 2

So Swordsman, same reasoning as with your last question. Pick any value x. If it has two values for y, then it isn't function (because you can't give me a definite answer of what f(x) is at that point).

If all values of x have unique y values, then it's a function.

Answer 3

I understand That.. its just i dont understand the way the charts are set up. how do i know what the X values are?

Answer 4

So see the line? Pick any part of the line, a point in it. Find the x and y coordinate of that point. That is the (x,y) coordinate there.

You cannot have two points on that line with the same x coordinate. Eg (0, 3) and (0,2). If you can find any two points like that, it isn't a function.

Answer 5

Looking at picture B. See when x = 0? What are the y values there?

Answer 6

2 and -2?

Answer 7

Yep, very good. So would that be a function?

Answer 8

no.. Becuase it cant be the same number value?

Answer 9

Exactly, well done! You can't have two identical x values. Now let's look at the first picture A. Can you see if that's a function or not?

Answer 10

so i can say c is wrong too?

Answer 11

That's right, good work.

Answer 12

so its a or d.. on d its just dots.. so does that mean i can cut out d.. and the answer would be a>?

Answer 13

Nope. For d there are only four unique points as you can see. But for part a, there are an infinite number of points (you can imagine how many dots there are joined together to make that line).

Answer 14

d can still be a function, but to prove it's not, you need to find an example where two x values are the same, can you think of any?

Answer 15

-4 and -2?

Answer 16

-2 only has one unique y value (-5), so that wouldn't proof it isn't a function. But you're right about -4, since that has two y values (both -1 and 5). So you've shown it isn't a function, well done.

Answer 17

oh.. on A its the same - and + number so on A B and C it cant be the function.. so that leaves D as the answer! Right?

Answer 18

D isn't a function. But A is. Because in A, you can pick any value x, and there is only one unique value of y. Try it and see if you can find where that isn't true. You shouldn't find anywhere.

Answer 19

*Face Palm* oh noes.. im so blonde!!! THANKS FOR THE HELP!! :D

Answer 20

No problem =)