• Mar 28th 2013, 07:07 PM
mathkid182
The points (−1, 2) and (−1, 1) satisfy a relation R, which of the following can we (definitely) conclude?

Select one:
a. R is a function
b. R is not a function
c. R is y=-1
d. R is x=-1
e. None of the above

• Mar 28th 2013, 07:56 PM
Paze
This is not a hard question. Tell us what you have tried so far.
• Mar 28th 2013, 08:34 PM
Prove It
Quote:

Originally Posted by mathkid182
The points (−1, 2) and (−1, 1) satisfy a relation R, which of the following can we (definitely) conclude?

Select one:
a. R is a function
b. R is not a function
c. R is y=-1
d. R is x=-1
e. None of the above

Do you understand that functions work by putting a number in and getting a single number out?

What's happening in your case with the number you're putting in? (i.e. x = -1)
• Mar 28th 2013, 08:41 PM
mathkid182
not to worry sorry i figured out that because it has the same -1 on both plots it is not a function.

The points (1, 3) and (2, 3) satisfy a relation R, which of the following can we (definitely) conclude?

Select one:
a. R is a function
b. R is not a function
c. R is y=3
d. R is a straight line
e. None of the above

I know its a straight line and is function but neither answers are right? what would be the right answer?
• Mar 28th 2013, 09:00 PM
Paze
Quote:

Originally Posted by mathkid182
not to worry sorry i figured out that because it has the same -1 on both plots it is not a function.

The points (1, 3) and (2, 3) satisfy a relation R, which of the following can we (definitely) conclude?

Select one:
a. R is a function
b. R is not a function
c. R is y=3
d. R is a straight line
e. None of the above

I know its a straight line and is function but neither answers are right? what would be the right answer?

Look at the co-ordinates you are given and see if you notice a trend.

Also, in the future, please post in the appropriate forum. You have posted in the calculus forum. This belongs to 'algebra'.
• Mar 29th 2013, 02:56 AM
emakarov
Quote:

Originally Posted by Paze
Look at the co-ordinates you are given and see if you notice a trend.

A trend is irrelevant to the possibility of making a definite conclusion.
• Mar 29th 2013, 05:48 AM
Ruun
Suposse that your given ordered pairs belong to the cartesian product that defines a function. Then they will be in the form $(x,f(x))$. Now recall the definition of a function, in particular about the uniqueness about $f(x)$
• Mar 29th 2013, 07:46 AM
HallsofIvy
Quote:

Originally Posted by mathkid182
not to worry sorry i figured out that because it has the same -1 on both plots it is not a function.

The points (1, 3) and (2, 3) satisfy a relation R, which of the following can we (definitely) conclude?

Select one:
a. R is a function
b. R is not a function
c. R is y=3
d. R is a straight line
e. None of the above

I know its a straight line and is function but neither answers are right? what would be the right answer?

No, you don't know either of those things. For example the relation containing pairs {(1, 3), (2, 3), (1, -3)} and y= x for x not equal to 1 or 2 is not a function nor a straight line but sastisfies the conditions. You seem to be under the impression that since we have both (1, 3) and (2, 3) we must have "y= 3" for all x. That is possible but not necessary.
• Mar 29th 2013, 09:51 AM
Paze
Quote:

Originally Posted by emakarov
A trend is irrelevant to the possibility of making a definite conclusion.

But by noticing the trend, you should be able to come up with a definite conclusion, yes?
• Mar 29th 2013, 10:47 AM
emakarov
Quote:

Originally Posted by Paze
But by noticing the trend, you should be able to come up with a definite conclusion, yes?

As HallsofIvy describes, in this case the trend is misleading. It does not follow that R has properties (a)-(d).
• Mar 29th 2013, 10:58 AM
Paze
Quote:

Originally Posted by emakarov
As HallsofIvy describes, in this case the trend is misleading. It does not follow that R has properties (a)-(d).

I don't understand. We have the points (1,3) and (2,3) and we are to conclude a relation between these points. y=3 in both points so how come this does not satisfy a 'relationship' between these two points? Nobody said anything about all x. Or maybe I am misunderstanding?
• Mar 29th 2013, 11:07 AM
emakarov
Quote:

Originally Posted by Paze
We have the points (1,3) and (2,3) and we are to conclude a relation between these points. y=3 in both points so how come this does not satisfy a 'relationship' between these two points? Nobody said anything about all x. Or maybe I am misunderstanding?

Yes, the question is about all x. That is, the question is about R as a whole, about all pairs (x, y) in R. And it asks not what type of R could contain (1, 3) and (2, 3), but what statements about R follow with necessity. Neither of statements (a)-(d) do.
• Mar 29th 2013, 11:13 AM
Hartlw
Quote:

Originally Posted by mathkid182
not to worry sorry i figured out that because it has the same -1 on both plots it is not a function.

The points (1, 3) and (2, 3) satisfy a relation R, which of the following can we (definitely) conclude?

Select one:
a. R is a function
b. R is not a function
c. R is y=3
d. R is a straight line
e. None of the above

I know its a straight line and is function but neither answers are right? what would be the right answer?

my 2cents worth:
a) and c).
R is not a straight line. Plot it. Does it look like a straight line? It looks like two points to me.