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05-18-2011, 03:25 AM #1
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Toaster
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Put Your Calculus Hat On (Help)

The Problem

y=((X+1)/(X-1))^4

Chain Rule + Quotient Rule:

y'=4((X+1)/(X-1))^3 (((1)(X-1)-(1)(X+1))/((X-1)^2))

Combining the terms, I get:

y'=-8((X+1)^3)/((X-1)^5)

BUT the book says(Notice the lack of negative):

y'=8((X+1)^3)/((X-1)^5)

So where did I get (Or lose) The negative.

There will probably be more questions farther on. I realize that It is hard to look at it in this form so maybe writing it out will help.

Thanks anyone!

Edit: I Think it MIGHT be a book typo.

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Last edited by Toaster; 05-18-2011 at 03:54 AM.

05-18-2011, 04:16 AM #2
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daguin
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Re: Put Your Calculus Hat On (Help)

CALCULUS HAT !

I don't even have an arithmetic hat

Peace,
dave
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05-18-2011, 04:44 AM #3
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Toaster
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Re: Put Your Calculus Hat On (Help)

Lol come on. This is a science forum, some few here have to know a little.
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05-18-2011, 05:25 AM #4
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Ezcal
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Re: Put Your Calculus Hat On (Help)

WolframAlpha and I agree with you, Toaster. It's a book typo.

WolframAlpha's Work Here
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05-18-2011, 07:39 AM #5
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Re: Put Your Calculus Hat On (Help)

It's been a looonnnggg time man but the negative just doesn't evaporate. I agree with you on the typo!
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05-18-2011, 06:27 PM #6
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Re: Put Your Calculus Hat On (Help)

Thanks, I thought I was going crazy. I have few more that I had no idea how to go about solving. The back of the book has the asnwers but not how to get them.

Here is one:
y=(cot(x^5))^7

y'=30x((1+(((x^2)+2)^5))^2)(((x^2)+2)^4)

You don't have to show the solving, just what rules in what steps... (Thats what has got me tied up.)

If anyone knows a site that shows how to solve I would be EXTREMELY grateful.

Thanks
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Last edited by Toaster; 05-18-2011 at 06:31 PM.

05-18-2011, 09:33 PM #7
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Re: Put Your Calculus Hat On (Help)

Well, we never had to deal with cot, csc or sec in my calc class, but it looks like you'd want to start with the chain rule, since you have a function (x^5) inside another function there.

WolframAlpha, by the way, is a great resource for basically all math problems. You basically plug in what you want... "derivative of (cot(x^5))^7" and it will spit out the answer. Most of the time you can even hit "Show Steps" and it'll walk you through how to solve it.
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05-18-2011, 10:55 PM #8
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Re: Put Your Calculus Hat On (Help)

K I will look it up. What confuses me is that the Wolf, and book answer are different, even though the Wolf answer looks a lot more reasonable.
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05-20-2011, 05:28 AM #9
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swimminsurfer256
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Re: Put Your Calculus Hat On (Help)

TI-89

nuff said. that got me through calc BC all those years ago
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