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January 27th, 2011, 09:05 AM   #1
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Radicals

I just wanted to know the answer to a specific question:

sqrt15 sqrt21 / sqrt5


The answer I got was 9sqrt7


Any help is greatly appreciated, thank you.

jrobbo
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January 27th, 2011, 09:13 AM   #2
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Re: Radicals

You are given:



Since we may write this as:

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January 27th, 2011, 09:14 AM   #3
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Re: Radicals

Since ?(15) = ?(5)*?(3), we can cancel the ?(5) from top and bottom and be left with
?(3)*?(21) =
?(3)*?(3)*?(7) = 3?(7)

And Mark strikes again!
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January 27th, 2011, 09:18 AM   #4
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Re: Radicals

Quote:
Originally Posted by The Chaz
...
And Mark strikes again!


It never hurts to have more than one way to look at a given problem.
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January 27th, 2011, 11:28 AM   #5
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Re: Radicals

... or more than one way to use the same "formula"!
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January 28th, 2011, 09:30 AM   #6
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Re: Radicals

thanks guys
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January 28th, 2011, 10:11 AM   #7
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Re: Radicals

You are welcome.
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February 10th, 2011, 04:13 AM   #8
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Re: Radicals

I did the same thing via video on my blog and youtube, but I won't include that bit. Here's a couple of other videos about radicals and why (and when) you can use them to do what we did here in this thread. I put these before and after my solution, so they are directly related, btw.

Rednecks falling in love explanation: http://www.youtube.com/user/idearella#p/u/2/jUqYlK7mPgg

Having stupid addition in the mix: http://www.youtube.com/user/idearella#p/u/0/Uawf6pgGG7o
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