From: Loyd <loydlin>
To: Teacher2Teacher Public Discussion
Date: 2002050105:54:48
Subject: Re: adding and multiplying radicals

On 2002050102:40:44, Pam Primiani wrote:
>	
>Sons text is of no help and have found little on the internet.  She
>wants them to factor to get their answer.  Example problems are
listed
>below.  Are there any rules to use as to when to place the number in
>front of the square root sign?
>no square root sign so will use sr to denote that
>sr of 20 + sr of -20
>

Yes, factor first:

sqrt(20)+sqrt(-20)
= sqrt(4x5)+sqrt(-1x4x5)
Then take out the square root of any perfect square such as 4 and
place the root in front of the radical:
2sqrt(5) + 2isqrt(5).


Note that the square root of -1 is called i in mathematics; except
electrical engineers call it j because i represents current to them.

If the radicals are like radicals, you can add them.  In the case
above, the answer is complex (imaginary because of the i) so you can't
combine them.

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