MEDAL!!!

Which set of ordered pairs represents a function?
A. (-2,1), (0,1), (1,-2), (3,4)
B. (-1,5), (-2,3), (-2,1), (-3,1)
C. (12,36), (9,27), (-6,30), (9, 18)
D. (3,17), (-2,11), (1,8), (3,5)

Question

MEDAL!!!


Which set of ordered pairs represents a function? 
A.  (-2,1), (0,1), (1,-2), (3,4)
B. (-1,5), (-2,3), (-2,1), (-3,1)
C. (12,36), (9,27), (-6,30), (9, 18)
D. (3,17), (-2,11), (1,8), (3,5)

calculusxy · Answer

@SolomonZelman

anonymous · Answer

Hi,
Do you know the definition of a function?

calculusxy · Answer

Here is my thinking: it's either a or c.

openstudier · Answer

A function is represented by a set of values where every x-value corresponds to EXACTLY one y-value.

anonymous · Answer

Firstly you need to know the definition of a function.
You can simply google it.

mathmale · Answer

What criteria are  you (calculusxy) using to identify functions?

calculusxy · Answer

Yes I have some idea of what a function is. Just like what @OpenStudier said, the x-value value needs to have only one y-value.

mathmale · Answer

and so if you find the same number more than once  as the first coordinates of points, you've got a relationship, not a function.

solomonzelman · Answer

mathmale, I think it is referring to a relation that would satisfy an explicit function in a form of y=f(x) ... that is typical for these questions

solomonzelman · Answer

oh, you said it already :D

mathmale · Answer

Please look at the set of possible answers and apply this criterion to select any that are functions.

anonymous · Answer

so if in a set you can find two ordered pairs which have same Xs and different Ys, then:
1) It is a function.
2)it is NOT  a function.
which choice is correct?

calculusxy · Answer

I know that it can't be B or D because in B -2 has two outputs and in D 3 has two outputs as well.

anonymous · Answer

so you already know the correct choice.

calculusxy · Answer

I am actually confused between A and C.

calculusxy · Answer

What can I do to distinguish the function from those two options?

openstudier · Answer

Hint: Answer choice C has two y-values for the x-value 9.

mathmale · Answer

If you've tentatively eliminated B and D, take a closer look at A and C and apply the criteria for functions to these two.  Which one, A or C, represents a function?

calculusxy · Answer

Oh wow. I didn't even analyze it so much as to notice that C is like A and D.

calculusxy · Answer

Sorry I meant B and D.

mathmale · Answer

Better go back and review the criteria, then.

calculusxy · Answer

So it has to be A right?

mathmale · Answer

Why?  Important that you be able to explain your choice.

mathmale · Answer

"I choose A because .....   ?

er.mohd.amir · Answer

option B ,C and D are not fuction since domain elements are same with differnt image.

calculusxy · Answer

Ok. So in B, C, and D the domains have more than one output (which indicates that this is not a function, instead it's a relationship). Since the ordered pairs in set A shows that each of the domain has only one range, it is best to choose this option because this is what a function should look like (one output for every input).

inkyvoyd · Answer

you should probably put in the question before putting in medal cause all I read was medal and that's all I care about

mathmale · Answer

Your "this is what a function should look like (one output for every input). " is the most accurate explanation.  "each of the domain has only one range" is not correct.  What you're saying here is that "each element of the domain is connected to (maps onto) exactly one element of the range.."     No function has 2 or more ranges.

anonymous · Answer

@mathmale after all, It's more polite not to speak or send messages while someone is answering a question until there's a problem or for helping with complementary points.