My Math Forum need some explanation about square roots
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 Algebra Pre-Algebra and Basic Algebra Math Forum

 April 22nd, 2016, 09:07 AM #1 Newbie   Joined: Apr 2016 From: outer space Posts: 15 Thanks: 4 need some explanation about square roots I know about roots and the quadratic formula, but I need some explanation about what was done here from the part where the square root of 8 became the square roots of 4 and 2 to the end of this, especially the third line. Last edited by skipjack; April 22nd, 2016 at 07:47 PM.
 April 22nd, 2016, 09:27 AM #2 Senior Member   Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics You may want to do some additional exercises on surds. It's important to have a good background in the arithmetic of surds before getting to quadratic equations. Mainly, the second line was about simplifying the part in the square root. 8 is made up of three factors 2 x 2 x 2, and you know that 2 x 2 is a square, so you can find the square root of 2 x 2 (i.e. 2) and move it outside the square root sign. $\displaystyle \sqrt 8 = \sqrt{4 \times 2} = \sqrt 4 \sqrt 2 = 2 \sqrt 2$. The remaining steps were about fraction reduction, the same way you'd reduce a fraction from, say, $\displaystyle \displaystyle{2 \over 4}$ to $\displaystyle \displaystyle{1 \over 2}$.
 April 22nd, 2016, 11:39 AM #3 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 Surely you know that 8= 4*2. And then $\displaystyle \sqrt{2*4}= \sqrt{2}\sqrt{4}$ and $\displaystyle \sqrt{4}= 2$. Putting those together, $\displaystyle \sqrt{8}= \sqrt{4*2}= 2\sqrt{2}$. Last edited by skipjack; April 22nd, 2016 at 07:45 PM.
 April 22nd, 2016, 03:12 PM #4 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,834 Thanks: 649 Math Focus: Yet to find out. Someone should make a macro for countryboy that converts [tex] to [math] when on MMF
April 22nd, 2016, 07:51 PM   #5
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Quote:
 Originally Posted by kate09 . . . especially the third line.
As "2" is appears in both the numerator and the denominator, it cancels. Did you mean to refer to this line?

April 23rd, 2016, 01:47 AM   #6
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Quote:
 Originally Posted by Joppy Someone should make a macro for countryboy that converts [tex] to [math] when on MMF
Is he from an SMF-based forum?

 April 23rd, 2016, 02:24 AM #7 Global Moderator   Joined: Dec 2006 Posts: 20,925 Thanks: 2203 I don't know of any mathematics forum using SMF.
April 23rd, 2016, 07:17 AM   #8
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Quote:
 Originally Posted by Joppy Someone should make a macro for countryboy that converts [tex] to [math] when on MMF
I sent a private message to him about using them. If his posts are edited, and he leaves and never looks back
at them, he probably wouldn't know that his way doesn't work on here.

May 12th, 2016, 03:48 PM   #9
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Quote:
 Originally Posted by skipjack I don't know of any mathematics forum using SMF.
A science forum in my country uses SMF, and it uses MimeTeX with codes (though it doesn't work anymore).

 May 14th, 2016, 06:29 AM #10 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 I was worried at first. The last thing I need is yet another math forum to spend time on! Fortunately that one was not in any language I read.

 Tags explanation, explenation, roots, square

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