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# DOMAIN OF x^2-1 Watch

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1. I've drew the graph for x^2 -.it cuts the x axis at -1 and 1 and it cuts y at -1. Why is the domain xer and not -1< g < 1 ?!! Is it because domain isn't restricted I'm confused how do I find the domain
2. The domain is the x values for which y values exist. Y values exist for every x value on that function.
3. (Original post by Jane122)
I've drew the graph for x^2 -.it cuts the x axis at -1 and 1 and it cuts y at -1. Why is the domain xer and not -1< g < 1 ?!! Is it because domain isn't restricted I'm confused how do I find the domain
The domain is the set of the possible inputs to the function, so on a graph it's all the x values that have a y value. Any number can be squared, and any x-coordinate in your graph has a y-coordinate.

To find the domain looks for numbers which can't be x values- eg: negative numbers can't be square rooted, and you can't divide by 0.
4. The domain of the function y=x^2-1 constitutes the values of x, for which y has a real value, the domain is therefore = -infinity < x < infinity
5. (Original post by SeanFM)
The domain is the x values for which y values exist. Y values exist for every x value on that function.
So it's always xer? I still don't get where I went wrong on that question like is it cos the domains not restricted?
6. (Original post by Prince David)
The domain of the function y=x^2-1 constitutes the values of x, for which y has a real value, the domain is therefore = -infinity < x < infinity
So it's always xer? Wb -1<f(x)<1
7. (Original post by Jane122)
So it's always xer? Wb -1<f(x)<1
For this function the domain is xER since any value of x gives a valid value for the function.
*You can choose to restrict a domain to a specific set of values (for example if you wish to restrict it to a 1 to 1 function it could be x > 0. The range of a function is the possible values for f(x) given the domain (possible x values), in this case f(x) is greater than or equal to -1
You could be asked to solve when the function is < 0 i.e. -1<f(x)<1

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8. (Original post by Jane122)
So it's always xer? I still don't get where I went wrong on that question like is it cos the domains not restricted?
The domain is not always all real values, it's just that for that particular equation the domain is not restricted. To work out the domain try to find values of x that can't be put into the equation, if there are some then the domain is restricted.

For example if you had then the domain is restricted to because you won't get a real answer if you input a negative value of x.
9. (Original post by Jane122)
So it's always xer? I still don't get where I went wrong on that question like is it cos the domains not restricted?
wtf is an xer

10. (Original post by sindyscape62)
The domain is not always all real values, it's just that for that particular equation the domain is not restricted. To work out the domain try to find values of x that can't be put into the equation, if there are some then the domain is restricted.

For example if you had then the domain is restricted to because you won't get a real answer if you input a negative value of x.
I drew the graph of x^2-1 and it cuts the x axis at 1 and -1. So wouldn't the domain be between 1 and -1? Why is it xer?
11. (Original post by Jane122)
I drew the graph of x^2-1 and it cuts the x axis at 1 and -1. So wouldn't the domain be between 1 and -1? Why is it xer?
The domain has nothing to do with when f(x) < 0.
As people have said a few time in this thread, the domain of a function is the the set of values that x is allowed to be.
12. (Original post by gdunne42)
The domain has nothing to do with when f(x) < 0.
As people have said a few time in this thread, the domain of a function is the the set of values that x is allowed to be.
I'm sorry but I'm really confused despite drawing the graph I can't figure out the domanin. I want someone to clear up my understanding as to why the domain is xer and not between -1 and 1.
13. (Original post by gdunne42)
The domain has nothing to do with when f(x) < 0.
As people have said a few time in this thread, the domain of a function is the the set of values that x is allowed to be.

Also with the graph of - root over x-3 whys the range < less than equal to 0 ?
14. (Original post by Jane122)
I'm sorry but I'm really confused despite drawing the graph I can't figure out the domanin. I want someone to clear up my understanding as to why the domain is xer and not between -1 and 1.
You are not clear on what a domain is - that's fine. People have defined it in the thread but as you are still stuck I would suggest asking your teacher about it going over the material in the textbook about it.
15. (Original post by Jane122)
I'm sorry but I'm really confused despite drawing the graph I can't figure out the domanin. I want someone to clear up my understanding as to why the domain is xer and not between -1 and 1.
OK, one last time.
Where it crosses the x axis has NOTHING to do with the domain of the function.
Can you enter x=2 into your function and generate a result for f(x) ?
x=10 ? x=-5 ?
Any positive or negative (real) value you could possibly choose can be put into your function and generate a value for f(x) therefore "x can be any real number" is the domain of this function.
16. (Original post by Jane122)
Also with the graph of - root over x-3 whys the range < less than equal to 0 ?
the range of a function states the possible values for y given the values allowed for x (the domain)

Since what you have typed isn't complete and it's unclear what the function and domain are I would be guessing if I tried to explain the answer you have stated.

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Updated: October 2, 2016
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