Question

If the relation is a function, list the domain and range. If the relation is not a function, choose "not a function".

C = {(9, 1) (8, -3) (7, 5) (-5, 3)}


Domain: {9, 8, 7, -5} Range: {1, -3, 5, 3}
Domain: {1, -3, 5, 3} Range: {9, 8, 7, -5} not a function

Answer 1

So, the first thing we need to ask ourselves is: What exactly ARE the domain and range?

The domain is all possible INPUTS for our function.
The range is all possible OUTPUTS for our function.

The question also asks us to specify if our relation is a function. How do we know if it is or not?

A function is any relation where we can get an unambiguous output for any input. A simpler way to say this is, if we put something in, we have to know exactly what we're getting out.

So: {(1, 2), (3, 2)} is a function. Inputs are on the left (or our x values, think back to geometry and Cartesian co-ordinates) and outputs are on the right. (y values). Our domain (all possible inputs) is "1 and 3". Our range (possible outputs) is "2". If we put 1 in, we know we get 2. If we put 3 in, we know we get 2. This is a function with the domain (1, 3) and the range (2).

However, {(2, 1), (2, 3)} is NOT a function. Our domain is (2) and our range is (1, 3). So what's changed? Well, now when we input our 2, we don't know what to output. Is it 1? Is it 3? There's no way to tell, so this isn't a function; it's output is NOT ambiguous.

So now that we've answered this, we can look at our own function.

C = {(9, 1) (8, -3) (7, 5) (-5, 3)}

So, what's our domain? Our domain is all possible inputs. (9, 8, 7, -5) Our range is all possible outputs. (1, -3, 5, 3)

Lastly before we put our answer in; is this a function? Well, for that, we ask ourselves if every input can be traced to one and only one output. In this case, it can, so we can feel free to put our answer in, as this relation IS a function.

Answer 2

THANK YOU SO MUCH. You made me understand the subject more, stupid teachers NEVER pay attention to their cyber students.

Answer 3

Happy to help :) Comments like yours make my day, to know I've not only answered a question, but furthered someone's understanding as well!

When I was learning functions, a great resource I used was Khan Academy. You may want to check it out yourself if you find that the way you're learning doesn't explain things as well as you'd like: https://www.khanacademy.org/math/algebra/algebra-functions

It has all kinds of mathematics in it. The only thing it sometimes lacks are questions difficult enough to truly prepare for an exam, but if you're taking another course, you should find it a fantastic resource to shore up your understanding of anything you're having trouble with.

Answer 4

I'm taking Algebra two, worst subject ever... I used to love math until it kept me up.. endless nights..

Answer 5

Well, the good news is that you're living in the best time ever to struggle with mathematics, with the massive amount of options available to help :) Khan Academy is only one of them, and you've clearly found this place. Hell, if all else fails, you can probably just Google it and come up with a ton of other options.

Mathsisfun is yet another resource that you can look at. It tends to be very good at helping you visualise things through graphics, from the little I've seen of it. So that's three places you can go for anything you're having difficulty with that the default course materials seem to stump you on :)

Answer 6

help me out... i posted another question. They talk another language I SWEAAAR.