Domain and Range Help

KillerNoodle

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Joined
Jan 19, 2011
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I missed the day the teacher went over how to find domain and range in class, and am now trying to do the homework.
The problem just post's a graph and says "find domain and range"
How do I go about doing this? I think the domain is (-3,2) and the range is (-inf,inf) but I don't know the reason why.

Here's the graph, for what it's worth.
grag.gif


Any help is much appreciated.
 
KillerNoodle said:
The problem just post's a graph and says "find domain and range"
How do I go about doing this? I think the domain is (-3,2) and the range is (-inf,inf)
but I don't know the reason why.

Here's the graph, for what it's worth.
grag.gif


Any help is much appreciated.

KillerNoodle,

the graph looks to be a limitation of the size of the portion of the xy-plane shown.

Because of that, I would have an arrow at each end of the curve to show that it extends
indefinitely in both directions.

If that's the case, then I would state that the domain and the range are both equal to the
interval (-oo, oo), including that there are no gaps for the x-values, and no gaps for the y-values.
 
Generally, when considering Doman and Range, start with \(\displaystyle (-\infty,\infty)\). After that, see what needs to be discarded.

{repaired}
 
Tkhunny means \(\displaystyle (-\infty , \infty )\)

I agree that often this is a quick way to find the domain, but sometimes it's easier to find it directly. For example with functions involving roots.
 
?? Example? What's indirect about assuming what it probably is, anyway?
 
When I said "directly" I didn't really mean it as the opposite of indirectly. All I'm really saying is this:

In a function such as \(\displaystyle f(x)=\frac{1}{x}\) it's easiest to "discard" \(\displaystyle 0\) from \(\displaystyle (-\infty , \infty)\).

In a function such as \(\displaystyle f(x)=\sqrt{x}\) I think it's easier to just to say that \(\displaystyle x\) has to be greater than or equal to \(\displaystyle 0\) (thus the domain is \(\displaystyle [0,\infty)\)), as opposed to discarding \(\displaystyle (-\infty , 0)\).
 
Ty for the help, that's what was throwing me off was that there weren't any arrows, and so I didn't know if it kept going or not.
I did learn that the dots mean it stopped, so I guess it's safe to say this one just keeps going?

Also, this is the exact graph from the textbook, and my teacher said in college algebra we need not use arrows anymore. Is he correct in saying this?
 
I think whether you use arrows or not is just a matter of personal taste. I would always put them in just to avoid the confusion that you just went through.
 
DrSteve said:
All I'm really saying is this:

Fair enough. Always, I am pleased that unique answers don't care how you find them.
 
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