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# C3 functions watch

1. http://www.examsolutions.net/a-level...y/paper.php#Q7

7c how can i do this? usually you put in the domain of the original function to give you the range which is the domain of the inverse but in this case i can't do that because you can't do so how can i do this one?
2. (Original post by bigdonger)
http://www.examsolutions.net/a-level...y/paper.php#Q7

7c how can i do this? usually you put in the domain of the original function to give you the range which is the domain of the inverse but in this case i can't do that because you can't do so how can i do this one?
What's the range of f(x)?
3. (Original post by bigdonger)
http://www.examsolutions.net/a-level...y/paper.php#Q7

7c how can i do this? usually you put in the domain of the original function to give you the range which is the domain of the inverse but in this case i can't do that because you can't do so how can i do this one?
look at behaviour of f as x gets closer and closer to 1/2
4. The domain of the inverse function is the same as the range of the original function.
5. (Original post by RDKGames)
What's the range of f(x)?
that's my point how can i do that? usually i would put 0.5 into f(x) but that doesn't work because you can't have 1/0 it doesn't work so how can i have a range for this?

(Original post by 13 1 20 8 42)
look at behaviour of f as x gets closer and closer to 1/2
if i put 1 in i get 1 out
if i put -1 in i get -1 out
if i put 1/4 in i get -2 out
if i put 1/3 in i get -3 out
if i put in 0.4 i get -5 out
if i put 0.45 in i get -10 out
if i put in 3/4 in i get 2 out
if i put 0.55 in i get 10 out

i can't see anything besides the fact tat when i get closer to 0.5 the range seems to be infinitely huge
6. (Original post by bigdonger;[url="tel:66453208")
66453208[/url]]that's my point how can i do that? usually i would put 0.5 into f(x) but that doesn't work because you can't have 1/0 it doesn't work so how can i have a range for this?

if i put 1 in i get 1 out
if i put -1 in i get -1 out
if i put 1/4 in i get -2 out
if i put 1/3 in i get -3 out
if i put in 0.4 i get -5 out
if i put 0.45 in i get -10 out
if i put in 3/4 in i get 2 out
if i put 0.55 in i get 10 out

i can't see anything besides the fact tat when i get closer to 0.5 the range seems to be infinitely huge
But that's exactly it. Range is everything real except 0.5.
7. (Original post by B_9710)
The domain of the inverse function is the same as the range of the original function.
I did just say this in my original post >.>
(Original post by RDKGames)
But that's exactly it. Range is everything real except 0.5.
No that's the domain which is stated in the question....
8. (Original post by bigdonger)
I did just say this in my original post >.>

No that's the domain which is stated in the question....
Sketch the graph then if you can't immediately find the range of f.
9. (Original post by bigdonger)
that's my point how can i do that? usually i would put 0.5 into f(x) but that doesn't work because you can't have 1/0 it doesn't work so how can i have a range for this?

if i put 1 in i get 1 out
if i put -1 in i get -1 out
if i put 1/4 in i get -2 out
if i put 1/3 in i get -3 out
if i put in 0.4 i get -5 out
if i put 0.45 in i get -10 out
if i put in 3/4 in i get 2 out
if i put 0.55 in i get 10 out

i can't see anything besides the fact tat when i get closer to 0.5 the range seems to be infinitely huge
Exactly, the range has no upper bound, only a lower bound, can you see what it is?
10. (Original post by B_9710)
Sketch the graph then if you can't immediately find the range of f.
ewww i hate sketching graphs especially stuff like this
(Original post by 13 1 20 8 42)
Exactly, the range has no upper bound, only a lower bound, can you see what it is?
i'm sure it doesnt have an upper or lower bound... if i put in numbers close but smaller than 0.5 i get big negative values if i put in numbers closer but bigger than 0.5 i get bit positive numbers so i'm not seeing anything here apart from the range could be something stupidly high
11. (Original post by bigdonger)
ewww i hate sketching graphs especially stuff like this

i'm sure it doesnt have an upper or lower bound... if i put in numbers close but smaller than 0.5 i get big negative values if i put in numbers closer but bigger than 0.5 i get bit positive numbers so i'm not seeing anything here apart from the range could be something stupidly high
But x > 1/2, read part a) again
edit: well not part a, start of the question
12. (Original post by 13 1 20 8 42)
But x > 1/2, read part a) again
edit: well not part a, start of the question
ah so what comes out the otherside are just ridiculously huge numbers
13. (Original post by bigdonger;[url="tel:66453380")
66453380[/url]]ewww i hate sketching graphs especially stuff like this

i'm sure it doesnt have an upper or lower bound... if i put in numbers close but smaller than 0.5 i get big negative values if i put in numbers closer but bigger than 0.5 i get bit positive numbers so i'm not seeing anything here apart from the range could be something stupidly high
Okay you are confusing me. Here's what's what. For original; domain x>0.5, range y>0. So for inverse the domain will be X>0
14. (Original post by RDKGames)
Okay you are confusing me. Here's what's what. For original; domain x>0.5, range y>0. So for inverse the domain will be X>0
wat where does y.0 come from... ?????????????
15. (Original post by bigdonger)
wat where does y.0 come from... ?????????????
That's the range...
16. Perhaps watch the exam solutions vid on the questions...

He explains it pretty well
17. (Original post by RDKGames)
That's the range...
and where does it come from?
18. (Original post by bigdonger;[url="tel:66453592")
66453592[/url]]and where does it come from?
Look at the equation. Nothing will make it equal 0 because numerator is 1 hence it cannot be equal 0. From the domain you can work out whether it is more or less than 0
19. (Original post by hellomynameisr)
Perhaps watch the exam solutions vid on the questions...

He explains it pretty well
i don't want to draw a graph everytime i have one of these questions, it takes too long
(Original post by RDKGames)
Look at the equation. Nothing will make it equal 0 because numerator is 1 hence it cannot be equal 0. From the domain you can work out whether it is more or less than 0
ok sounds good
20. (Original post by bigdonger)
i don't want to draw a graph everytime i have one of these questions, it takes too long
You should practice your graph-sketching skills then, simple ones like these shouldn't be taking "too long", once you have some intuition and understanding down, then you can stop drawing graphs everytime you have one of these questions, for now - draw the graphs, seriously.

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