A root can only have a negative value if it is an odd root

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eloka: Junior | Next Rank: 30 Posts; Posts: 17; Joined: Mon May 17, 2010 8:16 pm; Location: Indonesia; GMAT Score:340

by eloka » Mon May 17, 2010 8:26 pm

and the base of the root is negative..(from Manhattan GMAT)

However, according to other gmat preps

root -1 or root -27 are imaginary number.

can we count any root imaginary number?

is imaginary number countable?

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Source: Beat The GMAT — Quantitative Reasoning | Mon May 17, 2010 8:26 pm

thinkpanther: Junior | Next Rank: 30 Posts; Posts: 20; Joined: Wed Feb 25, 2009 9:59 pmFollowed by: 1 member; Thanked: 1 times; GMAT Score:730

by thinkpanther » Tue May 18, 2010 11:01 am

Hi Eloka,

Below is how this works:

root of a negative number is real only if the root is odd, (3,5,7,9 etc)

Eg. cube root (-27) or (-27)^(1/3) = -3 or -3*-3*-3 = -27

root in general english refers to square root or ^(1/2)

sqrt(-27) or sqrt(-1) is not allowed and hence imaginary

HTH

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