will'o'wisp
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http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf

oh boy do i love these

So for 6a is the domain of f^{-1} is\ x\in \mathbb{R} x<2??
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the bear
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(Original post by will'o'wisp)
...
the domain f^{-1} is the same as the range of f
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will'o'wisp
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(Original post by the bear)
the domain f^{-1} is the same as the range of f
so did i work it out right or is it the same as the domain because you can't have -ve logs
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will'o'wisp
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(Original post by the bear)
the domain f^{-1} is the same as the range of f
but the best bit is when the mark scheme doesn't even give u an answer
http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf
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the bear
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(Original post by will'o'wisp)
so did i work it out right or is it the same as the domain because you can't have -ve logs
the domain of f is given as x<2, x e R, which means that ( 4 - 2x ) will always be greater than 0, thus the ln of (4 - 2x ) will go from - infinity to infinity ... this will be the range of f and also the domain of f-1
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will'o'wisp
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(Original post by the bear)
the domain of f is given as x<2, x e R, which means that ( 4 - 2x ) will always be greater than 0, thus the ln of (4 - 2x ) will go from - infinity to infinity ... this will be the range of f and also the domain of f-1
but how does it work?

if i put a number slightly less than 2 in i'll get ln(????)=almost 0

the further i go down the number scale ln(????????) gets bigger

so how can i get a -infinity out of this? there is no real number i can think of which will allow me to get -infinity out of ln(4-2x)
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the bear
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the bear
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(Original post by will'o'wisp)
but how does it work?

if i put a number slightly less than 2 in i'll get ln(????)=almost 0

the further i go down the number scale ln(????????) gets bigger

so how can i get a -infinity out of this? there is no real number i can think of which will allow me to get -infinity out of ln(4-2x)
^^^
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will'o'wisp
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(Original post by the bear)
^^^
so i'm saying x \in \mathbb{R}\ f(x)&gt;0???
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the bear
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grrr ******** latex

the domain of the inverse of f is just x is all Real Numbers.
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B_9710
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The domain is  \mathbb{R} since the range of f is  \mathbb{R} .
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will'o'wisp
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(Original post by the bear)
grrr ******** latex

the domain of the inverse of f is just x is all Real Numbers.
????? but i don't get it ;_________;
(Original post by B_9710)
The domain is  \mathbb{R} since the range of f is  \mathbb{R} .
ok but you can't have an ln(- anything) in here it doesn't work
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B_9710
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(Original post by will'o'wisp)
so i'm saying x \in \mathbb{R}\ f(x)&gt;0???
Perhaps it would help if you make a sketch of the graph pf  y=\ln (4-2x) .
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the bear
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the domain of the inverse is the x values which work with the inverse... they do not have to work with the original function.
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will'o'wisp
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#15
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(Original post by B_9710)
Perhaps it would help if you make a sketch of the graph pf  y=\ln (4-2x) .
hmmm so for any log/ln graph the range will always be [latex x\in \mathbb{R}[/latex]?

I've just drawn the graph now bc it asks me to in part c
(Original post by the bear)
the domain of the inverse is the x values which work with the inverse... they do not have to work with the original function.
ok?
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