Domain + Range

[elly39951]

My question is how do you find out the domain and/ or range of horizontal or vertical lines?
I have attached a picture, so how would you find the domain and range of lines e.g. 1 (red colour - vertical) and 7 (purple colour - horizontal)?

[alondouek]

All you need to do is read off the graph.

A domain is all included x-values of a function, while a range is all included y-values.

So, for example, the domain of 'line 1' is only [22,22] (as it only occupies one x-value, 22), though its range is [9,16], as it occupies the y-values of 9 through to 16 inclusive.

Hope I helped

[elly39951]

What do you mean by [22,22] --> would my teacher think that this is a point on the graph?

should it be [-22, -22]? (can you just put [-22])?

and for line 7 then would the domain be [-14, -10] and the range would be [4,4]??

[Homer]

domain is how far it goes left to right and range is high it goes. Also alondouek just a typo but domain should be {x:x=-22}  and yes line 7 seems right

[alondouek]

Yeah, my bad the domain for line 1 is [-22,-22] Sorry

And your teacher wouldn't consider this a point on the graph, as a perfectly vertical line (as line 1 is) can occupy this domain, but have an infinite range i.e. (-inf,inf).

For line 7, it's very similar: The domain would be [-14,-10], as those are the x-values occupied by the function; meanwhile the range is [4,4], as it is the only y-value occupied.

[elly39951]

so if {x:x=-22}
then for line 7,

{y:y=4}

??

[alondouek]

Yep!

[Stick]

My question is how do you find out the domain and/ or range of horizontal or vertical lines?
I have attached a picture, so how would you find the domain and range of lines e.g. 1 (red colour - vertical) and 7 (purple colour - horizontal)?

I did Graphs and Relations and I got a 50 for this subject and this is the first time I have ever come across a domain and range question in Further. I doubt that this would even come up as you haven't been taught correct notation, and notation is not part of the Further Mathematics course.

This is incredibly unusual.

[elly39951]

^
This thing has confused me??! (my last post)

[Stick]

Yeah, that's right. Do me a favour and check this with your school teacher. I did a huge amount of trial exams and SACs and have never come across this before.

[elly39951]

This is a copy of my assignment! Can u tell me if I am doing the correct thing, for what I am asking about?

[alondouek]

yeah, the example given is just a different form of notation. I have to say, I wouldn't have expected to see this sort of thing in a Further assignment... more methods, really...

[elly39951]

So how would you write the notation in the assignments format?

I didn't understand why when they had y=8 4 < x <(smaller than or equal to) 8 ??

coz shouldn't they both be smaller than or equal to??


And if you are doing the domain for a vertical line do you just sub in y, so

e.g. x=2 3<(smaller than or equal to) y <(smaller than or equal to) 5

etc...??

[elly39951]

wait that doesn't make sense coz the domain is x-values so how do you write it in the format they want it?
From e.g {x:x=12}???

[elly39951]

^
^
Or does it coz it is saying the y values??