Question

Which set of ordered pairs in the form of (x, y) does not represent a function of x?

{(1, 1.5), (2, 1.5), (3, 1.5), (4, 1.5)}

{(0, 1.5), (3, 2.5), (1, 3.3), (1, 4.5)}

{(1, 1.5), (–1, 1.5), (2, 2.5), (–2, 2.5)}

{(1, 1.5), (–1, –1.5), (2, 2.5), (–2, 2.5)}

Answer 1

A function must match each x value to EXACTLY one y value. You can't have one ordered pair that matches an x to one thing, and another ordered pair that matches the SAME x to a DIFFERENT y.

Answer 2

I teach it as: "it is a function if it is true that, IF you KNOW x, you KNOW y." That is, once you know what x is, you know exactly what y is...... there is no, "well, y is EITHER this OR that." Knowing x means that you KNOW y.

Answer 3

For which set of ordered pairs above is that NOT true?

Answer 4

Would it then be, {(1, 1.5), (–1, 1.5), (2, 2.5), (–2, 2.5)}, the third answer?

Answer 5

Can you tell me which two pairs (x,y) are in that set, such that the SAME x value is matched to two DIFFERENT y values?

That's what you're looking for.

Answer 6

In other words: if this is my set or ordered pairs...

{(1, 1.5), (–1, 1.5), (2, 2.5), (–2, 2.5)}

Can I give you an x value, such that you will be unsure what the y value is? such that you can't be sure which ordered pair I'm looking at?

Answer 7

Yes.

Answer 8

Really? which one.

TELL ME what x value is paired with two different y-values, in that set, please.

Answer 9

Maybe not because the x value, 1 are negative and positive and the same with the 2.

Answer 10

Right. There are 4 DIFFERENT x values there, so certainly, there are no TWO pairs that match the SAME x to two DIFFERENT y's, right?

so look at your choices again. Remember what you are looking for.

Answer 11

What will make a set of ordered pairs NOT be a function??

It is, when there are TWO ordered pairs with the SAME x value but two DIFFERENT y values.

So it is NOT true, in that case, that "if you know x, you know y". Not for EVERY x.

Answer 12

{(1, 1.5), (–1, 1.5), (2, 2.5), (–2, 2.5)}
Does not reprensent a funtion of x?

Answer 13

didnt we just talk about that one??

Is there an x value in ANY of those ordered pairs, that appears in a DIFFERENT ordered pair, matched to a DIFFERENT value of y?

Answer 14

You know which coordinate is x, and which is y, in an ordered pair, right?

(x, y)

You are looking for a set where you have at least one FIRST COORDINATE (x) that is paired with two DIFFERENT SECOND COORDINATES (y's).

Answer 15

Then would it be {(1, 1.5), (2, 1.5), (3, 1.5), (4, 1.5)}
because they're all different?

Answer 16

Because all the x's are different?

Answer 17

All of the x's are different in {(1, 1.5), (–1, 1.5), (2, 2.5), (–2, 2.5)}, also.

Answer 18

The x's all being different does not make it NOT a function

Remember, you are looking for the set that is NOT a FUNCTION. not one that IS a function.

3 of these choices are functions. One is not.

Answer 19

You find the one that is NOT a function, by finding the one where you have the SAME x paired with two DIFFERENT y's.

Answer 20

If all the x's are different, then that certainly CAN'T be it. if every ordered pair has a different value for x, then there certainly aren't two ordered pairs that have the same x matched to 2 different y's... because there aren't even two ordered pairs that have the same x, to begin with.

Answer 21

None of the ones listed have the same x though.

Answer 22

Not true. Look again.

Do you know which coordinate of an ordered pair is x, and which is y??

Answer 23

{(0, 1.5), (3, 2.5), (1, 3.3), (1, 4.5)}?

Answer 24

DING DING DING!! That's it! :)

\({(0, 1.5), (3, 2.5), (\color{red}1, 3.3), (\color{red}1, 4.5)}\)

1 is paired with 3.3, and also with 4.5. So this is NOT a function. :)

Answer 25

If I said to you "I'm looking at an ordered pair with x=1, what is y?" you could not be sure.

Answer 26

Whoa! Thanks for your patience. Very slow at Algebra 2.

Answer 27

You're welcome; you stuck with it and if you now understand this problem that's what counts. :)