Composite Functions

DaveRobinsonUK · 2010-06-14 06:45:05

Hi Guys.

I have just learned about composite functions in my book and followed it, what I thought was o.k,
then I had a go at one of the questions and my answer is out, what looks to be slightly, though
I have a feeling is quite a way out.

Here is the question

find the composite function

where and

I get

though the book gives

bit of a bummer "so close, yet so far";)

Thanks David

bobbym · 2010-06-14 08:56:52

Hi Dave;

I am not geting either of those answers. I am getting 18x^2 + 33x + 15

Also, Dave check here for more:

http://www.mathsisfun.com/sets/function … ition.html

soroban · 2010-06-14 09:07:59

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .↑

. . . . .

.

DaveRobinsonUK · 2010-06-14 19:33:15

Hi Bobby and Soroban

Ahh, I see what I have done. For some reason I have added the 2 to make 10, rather that
subtract to get 6. So the 3 can't be taken out of the brackets completely, leaving that 10
instead of the 2 that it should be.

Thanks for the link Bobby it's great and I have also been looking for good notes on set builder
notation. You can hardley understand anything from Wikipedia.

bobbym · 2010-06-14 19:36:33

Hi Dave;

Wikipedia can be tough for everyone.

Here is page on set builder notation:

http://www.mathsisfun.com/sets/set-buil … ation.html

DaveRobinsonUK · 2010-06-14 19:55:30

Hi Bobby

Very Cool, I was also glad of the page on Domains and Ranges. My book has info about this
though it does not mention Codomains.

bobbym · 2010-06-14 20:23:05

There is some good stuff in there.

You can hardley understand anything from Wikipedia.

Yea, they can enigmatic too. I was just looking at a page where someone wrote about a documentary. Not only was it biased it was incorrect in spots. Then I did some work for them on their page for this forum. They deleted all my comments. And they were all complimentary and accurate. What, I was too nice? Should I have thrown some bias in there?

Sometimes I think they can use a name change, Wackipedia, Wimpipedia, Worstipedia, Impedia, Igottapedia...

DaveRobinsonUK · 2010-06-14 22:38:25

It's like you say, you can put amendments to increase the accuracy of the document and if the person
who originated it doesn't like it for whatever reason (probably due to their ignorance being exposed) they
can change it back. That doesn't say much for the overall accuracy of the information contained on the site.

Still, I suppose it has it's uses, as long as you don't take it too seriously. "Impedia"

Crockipedia, Erratipedia, Faultipedia, Confusipedia

bobbym · 2010-06-14 22:43:20

Hi Dave;

Hey, those are better than mine!

DaveRobinsonUK · 2010-06-14 22:47:50

I must confess I cheated a bit and used a thesaurus

bobbym · 2010-06-14 22:52:24

they can change it back.

I didn't know that the original author could change it back. So, what is the point of editing it, if he doesn't like it and there is a good chance of that. He is certainly going to undo it.

DaveRobinsonUK · 2010-06-14 23:17:21

I don't know if there is any truth in it for definate, though I have read in the past that the documents have
an owner. I think it is to guard against people purposely making changes that are false. I suppose it makes
sense from that point of view, but not if the information they are putting up there is incorrect in the first place.

bobbym · 2010-06-14 23:26:00

All in all they do a good job, but not at an introductory level.

Anyway, the MIF pages are much easier to grasp especially as a first exposure.

Avon · 2010-06-15 10:25:15

Articles on Wikipedia do not have owners. If anyone can edit an article then obviously anyone can edit the article to return it to an earlier state.

The threshold for inclusion in Wikipedia is verifiability, not truth. It doesn't matter whether or not what you wrote is correct; the reader should be able to verify statements made in the article by consulting the
reliable sources given for them.

DaveRobinsonUK · 2010-06-15 19:28:50

Cool... It does say that it is a common mistake people make, and I did read that in the local parish rag

Must admit that is the first time I have read any of that, with me not really being qualified to write about
anything. I just use it for a reference.

bobbym · 2010-06-15 19:41:27

Finding that out, though I suspected it is even worse. In my opinion it is awful to let just anyone remove material. Like I said I wrote a small review for this forum. Just facts, number of members, numbers of moderators, friendly people etc and mentioned mathopolis. Came back 2-3 days later it was all removed. The editor remained anonymous, which I hate.

Then just a day a day or two ago I came across a page, pure vindictiveness, biased comments a few errors also anonymous. Other authoritative sites force you to come up with a name at least when you enter or remove information.

DaveRobinsonUK · 2010-06-15 19:43:39

Anyway.. Back to the origianal problem.

I went through the 4 questions on MIF, thought cool and went back to my book
and came straight across this, I don't get the same answer and I ran it through
Maple and it gets the same answer I do, so I am stuck again.

find

I and Maple get

the book on the other hand gets

DaveRobinsonUK · 2010-06-15 19:45:57

Hi Bobby

Thats really bad, especially when it is vindictive. There should be no room for that.

bobbym · 2010-06-15 20:06:36

Hi Dave;

I should say that vindictive is a matter of opinion, if you are writing a page for them and you are supporting their beliefs than naturally they are going to assert that it is not vindictive. The best comment I have heard about their math pages is, "Wikipedia, is good if you already know the subject well. Better if you already everything that is on that page."

bobbym · 2010-06-15 21:23:42

Hi Dave;

Sorry. I didn't see your problem. Back to work we go.

the book on the other hand gets

Of course maple is right!

If

then your book would be right.

What is the name of the book?

DaveRobinsonUK · 2010-06-17 00:40:53

Hi Bobby

Sorry for the delay, had to nip out to Chichester.

The book is Calculus - Concepts and Contexts, by James Stewart.

I got it about 10 yrs ago and have only just started using it

bobbym · 2010-06-17 04:55:20

Hi DaveRobinsonUK;

By Stewart? Really, he is known for his accuracy. I have it too. Haven't looked at it yet because I prefer the Leitholdt or Smail book. Or rather I have grown used to them.

DaveRobinsonUK · 2010-06-17 05:47:45

It's quite big isn't it. Very beautiful too aesthetically as books go. Although I have only recently
been in a position to understand it, it has always been on of my prized possessions. I always
wanted to understand its contents which is another of the driving factors behind all this work.
There are many.

You recommend checking out the others then?

I think even if the solutions are different, the expainations and examples are top notch.

DaveRobinsonUK · 2010-06-17 06:02:25

Darn.. I thought I saw it for a second then, when checking and looking a the
answer in the book, so I worked it through but just came up with the same

I don't know, maybe it is just something that slipped past the copy readers.

bobbym · 2010-06-17 06:08:47

Hi Dave;

You recommend checking out the others then?

No, I am not recommending that. It is a fine book and all books contain typos and such. I know the feeling you are describing. The feeling of holding a book in your hands that you desperately want to understand but it takes a good potion of your life...

I think even if the solutions are different, the expainations and examples are top notch.

Also I would never steer anyone away from something that touched them. When I find such a book, that explains it to me then I never let go of it. Believe me when you are ignorant like me you have to look through tons of stuff to get 1 line of knowledge that you say, "I understand that, I think"

Also I notice that it touches you artistically. Keep the book!

It is interesting, my 2 mainstays Leitholdt and Smail are really ugly books. They are ugly to look at. Your comments made me think about why I ever picked them up to begin with. Don't know why I thought I preferred them?

Math Is Fun Forum

#1 2010-06-14 06:45:05

Composite Functions

#2 2010-06-14 08:56:52

Re: Composite Functions

#3 2010-06-14 09:07:59

Re: Composite Functions

#4 2010-06-14 19:33:15

Re: Composite Functions

#5 2010-06-14 19:36:33

Re: Composite Functions

#6 2010-06-14 19:55:30

Re: Composite Functions

#7 2010-06-14 20:23:05

Re: Composite Functions

#8 2010-06-14 22:38:25

Re: Composite Functions

#9 2010-06-14 22:43:20

Re: Composite Functions

#10 2010-06-14 22:47:50

Re: Composite Functions

#11 2010-06-14 22:52:24

Re: Composite Functions

#12 2010-06-14 23:17:21

Re: Composite Functions

#13 2010-06-14 23:26:00

Re: Composite Functions

#14 2010-06-15 10:25:15

Re: Composite Functions

#15 2010-06-15 19:28:50

Re: Composite Functions

#16 2010-06-15 19:41:27

Re: Composite Functions

#17 2010-06-15 19:43:39

Re: Composite Functions

#18 2010-06-15 19:45:57

Re: Composite Functions

#19 2010-06-15 20:06:36

Re: Composite Functions

#20 2010-06-15 21:23:42

Re: Composite Functions

#21 2010-06-17 00:40:53

Re: Composite Functions

#22 2010-06-17 04:55:20

Re: Composite Functions

#23 2010-06-17 05:47:45

Re: Composite Functions

#24 2010-06-17 06:02:25

Re: Composite Functions

#25 2010-06-17 06:08:47

Re: Composite Functions

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