# C3 functions

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Thread starter 4 years ago
#1
http://www.examsolutions.net/a-level...e/paper.php#Q4
part c
i got for the inverse which told me that it's a graph of translated on unit down

so i thought the range was

but it's not why is that?
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4 years ago
#2
(Original post by thegreatwhale;[url="tel:66469010")
66469010[/url]]http://www.examsolutions.net/a-level...e/paper.php#Q4
part c
i got for the inverse which told me that it's a graph of translated on unit down

so i thought the range was

but it's not why is that?
Because it links into the domain of the original function. Do you agree that the range of f(x) is less than 1/4?
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Thread starter 4 years ago
#3
(Original post by RDKGames)
Because it links into the domain of the original function. Do you agree that the range of f(x) is less than 1/4?
i don't quite understand...
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4 years ago
#4
(Original post by thegreatwhale;[url="tel:66469846")
66469846[/url]]i don't quite understand...
Sketch f(x) for X>3 and tell me the range that you find
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Thread starter 4 years ago
#5
(Original post by RDKGames)
Sketch f(x) for X>3 and tell me the range that you find
i've sketched it but i don't know how i can get the range from it....
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4 years ago
#6
(Original post by thegreatwhale;[url="tel:66470300")
66470300[/url]]i've sketched it but i don't know how i can get the range from it....
Plug in X=3 and the range is everything less than that answer. Hence why you exclude the equal bit, JUST less than. So range is everything less than f(3)
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Thread starter 4 years ago
#7
(Original post by RDKGames)
Plug in X=3 and the range is everything less than that answer. Hence why you exclude the equal bit, JUST less than. So range is everything less than f(3)
so x<3 ???
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4 years ago
#8
(Original post by thegreatwhale;[url="tel:66470388")
66470388[/url]]so x<3 ???
Are you getting confused between range and domain? Domain is what you are allowed to PLUG IN, range is what you get out as a result of plugging in the domain. So when you plug in X=3, you get 1/4. From your sketch you should see that as X increases from 3, the y value gets smaller and smaller thus the range is less than 1/4.

For the inverse, the domain the range of the original therefore the domain would be X<1/4 for the inverse.
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Thread starter 4 years ago
#9
(Original post by RDKGames)
Are you getting confused between range and domain? Domain is what you are allowed to PLUG IN, range is what you get out as a result of plugging in the domain. So when you plug in X=3, you get 1/4. From your sketch you should see that as X increases from 3, the y value gets smaller and smaller thus the range is less than 1/4.

For the inverse, the domain the range of the original therefore the domain would be X<1/4 for the inverse.
if i plug in 3 into i get not 0.25 >.>
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4 years ago
#10
(Original post by thegreatwhale;[url="tel:66470630")
66470630[/url]]if i plug in 3 into i get not 0.25 >.>
I said into f(x), you are plugging it into f-1(X)
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Thread starter 4 years ago
#11
(Original post by RDKGames)
I said into f(x), you are plugging it into f-1(X)
oh shintezewizel that's why i got a weird answer.... ah thanks so f(x)>0.25 ??
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4 years ago
#12

Hence answer to part c is between 0 and 1/4 for x

The 0 comes from the fact that the range for the original function is between 0 and 1/4; it never reaches 0.

Posted from TSR Mobile
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4 years ago
#13
(Original post by thegreatwhale;[url="tel:66470806")
66470806[/url]]oh shintezewizel that's why i got a weird answer.... ah thanks so f(x)>0.25 ??
No, less than that, observe your sketch for X>3 (assuming you got it right)
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Thread starter 4 years ago
#14
(Original post by RDKGames)
No, less than that, observe your sketch for X>3 (assuming you got it right)
tried looking at the graph for a while and the graph isn't very tall but goes on long for "infinity" but the range is the height so it's from 0 to 1/4 ???
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4 years ago
#15
(Original post by thegreatwhale)
tried looking at the graph for a while and the graph isn't very tall but goes on long for "infinity" but the range is the height so it's from 0 to 1/4 ???
Exactly. So that becomes the domain for its inverse then.
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Thread starter 4 years ago
#16
(Original post by RDKGames)
Exactly. So that becomes the domain for its inverse then.
thanks a bunch
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