Author Topic: Additional Math Help HERE ONLY...!  (Read 75503 times)

holtadit

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Re: Additional Math Help HERE ONLY...!
« Reply #210 on: May 30, 2010, 10:05:49 am »
I am experiencing some major difficulty in finding the inverse of a fuction, domain and range, would anyone be kind enough to help out ?

I can help with inverse of function - thats within my syllabus.

Offline J.Darren

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Re: Additional Math Help HERE ONLY...!
« Reply #211 on: May 30, 2010, 10:18:46 am »
I can help with inverse of function - thats within my syllabus.
Hmm ... what about exponential functions ?
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holtadit

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Re: Additional Math Help HERE ONLY...!
« Reply #212 on: May 30, 2010, 10:19:23 am »
Hmm ... what about exponential functions ?

Let me see an example.

Offline J.Darren

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Re: Additional Math Help HERE ONLY...!
« Reply #213 on: May 30, 2010, 10:21:00 am »
Let me see an example.
A function f is defined by f (x) = e^(x–1), where x > 0.
(i) State the range of f.
(ii) Find an expression for f –1.
(iii) State the domain of f –1.
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holtadit

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Re: Additional Math Help HERE ONLY...!
« Reply #214 on: May 30, 2010, 10:26:33 am »
Sorry Darren, but this is way out of my depth.

I do normal mathematics. Wish I could help you out.

Just hang in there; someone will be along to help you out ;)

Offline cooldude

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Re: Additional Math Help HERE ONLY...!
« Reply #215 on: May 30, 2010, 10:55:26 am »
Sorry Darren, but this is way out of my depth.

I do normal mathematics. Wish I could help you out.

Just hang in there; someone will be along to help you out ;)

l) okay substitute the value of 0 in the function-->
therefore f(0)=e^-1=0.368
therefore f(x)>0.368
we substitute the value of 0 because this is the least value in the domain, i know that 0 is not included, you can take something like 0.000000000000000001, but 0 is better. or we can use differentiation to find the minimum value of the function, d/dx (e^(x-1))=e^(x-1), therefore at 0 it is 0.368, therefore since this is the minimum value every value of y will be greater than 0.368, therefore the range is f(x)>0.368
ii) let f(x)=y,
now y=e^(x-1)
take log on both sides (to find the inverse we have to make x the subject)
ln y=x-1
x=ln y + 1
therefore f^-1(x)=ln x + 1
iii) the domain of f^-1(x)=range of f(x), therefore the domain is x>0.368

Offline J.Darren

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Re: Additional Math Help HERE ONLY...!
« Reply #216 on: May 30, 2010, 11:08:09 am »
l) okay substitute the value of 0 in the function-->
therefore f(0)=e^-1=0.368
therefore f(x)>0.368
we substitute the value of 0 because this is the least value in the domain, i know that 0 is not included, you can take something like 0.000000000000000001, but 0 is better. or we can use differentiation to find the minimum value of the function, d/dx (e^(x-1))=e^(x-1), therefore at 0 it is 0.368, therefore since this is the minimum value every value of y will be greater than 0.368, therefore the range is f(x)>0.368
ii) let f(x)=y,
now y=e^(x-1)
take log on both sides (to find the inverse we have to make x the subject)
ln y=x-1
x=ln y + 1
therefore f^-1(x)=ln x + 1
iii) the domain of f^-1(x)=range of f(x), therefore the domain is x>0.368

Thanks mate, although I don't quite get the final bit RE: domain of the inverse function = range of the function ...

By the way what would the inverse function look like if the original function is, say for example, ln (x-1) ?
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Offline J.Darren

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Re: Additional Math Help HERE ONLY...!
« Reply #217 on: May 30, 2010, 11:10:34 am »
By the way guys I have posted a list containing the rules of differntiation and integration, would you be kind enough to proof-read it to ensure that I have not left out anything ?

https://studentforums.biz/index.php/topic,8457.0.html
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Offline Ghost Of Highbury

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Re: Additional Math Help HERE ONLY...!
« Reply #218 on: May 30, 2010, 11:21:52 am »
Thanks mate, although I don't quite get the final bit RE: domain of the inverse function = range of the function ...

By the way what would the inverse function look like if the original function is, say for example, ln (x-1) ?

the inverse of any graph f(x) is the graph under reflection along y=x.
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Offline cooldude

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Re: Additional Math Help HERE ONLY...!
« Reply #219 on: May 30, 2010, 11:22:41 am »
Thanks mate, although I don't quite get the final bit RE: domain of the inverse function = range of the function ...

By the way what would the inverse function look like if the original function is, say for example, ln (x-1) ?

yep, the same applies (vice-versa) --> the range of an inverse function = to the domain of the function
and the reason is given by aadi
« Last Edit: May 30, 2010, 11:37:57 am by cooldude »

Offline Ghost Of Highbury

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Re: Additional Math Help HERE ONLY...!
« Reply #220 on: May 30, 2010, 11:24:50 am »
yep, as aadi says and the same applies the range of an inverse function is the domain of the function and the reason is given by aadi

exactly. wen is ur add. math exam darren?
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Offline J.Darren

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Re: Additional Math Help HERE ONLY...!
« Reply #221 on: May 30, 2010, 11:40:27 am »
exactly. wen is ur add. math exam darren?
The week after, same as you guys I believe ...
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Offline cooldude

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Re: Additional Math Help HERE ONLY...!
« Reply #222 on: May 30, 2010, 11:41:56 am »
The week after, same as you guys I believe ...

lol dude, aadi gave his add maths in nov 09 and i didnt give it all  :D

Offline syedz123

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Re: Additional Math Help HERE ONLY...!
« Reply #223 on: May 31, 2010, 04:21:56 pm »
am quite a week student in add math...can sum1 plz xplain question 12 second one on velocity for me...its may/june 09 p1...


I still have accouting,chems litt n econs n add math left so i wont b able to do alot of pp for add maths...can any1 plz recommend which yrs i shuld do..like gud hard papers...atleast 3 yrs plz apart 4rm 09 Thanks

Offline J.Darren

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Re: Additional Math Help HERE ONLY...!
« Reply #224 on: May 31, 2010, 05:00:52 pm »
am quite a week student in add math...can sum1 plz xplain question 12 second one on velocity for me...its may/june 09 p1...


I still have accouting,chems litt n econs n add math left so i wont b able to do alot of pp for add maths...can any1 plz recommend which yrs i shuld do..like gud hard papers...atleast 3 yrs plz apart 4rm 09 Thanks
If I were you I would do Add Maths over the others, Economics paper 2 is all about recital, Chemistry Paper 3 - You either know or you don't, understanding the concept is the key.
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