gmatpapa wrote:
sudhir18n wrote:
On the gmat square root of 4 will always be positive 2 .
hope this helps.
I seriously doubt that.. You can never say that conclusively.
If nothing is mentioned about x, then sqrt x is always equal to + or - x. This is, in fact, one of the favorite traps of GMAT..
In this question , since we're given that both m and n are positive, we can conclusively say that the outcome will be positive 10.
For all real numbers x
\sqrt{(x^2)}=|x|=x, if x>=0
=-x if x<0
which means sqrt of 4 will be always 2=>the absolute value
Source: wikipedia
https://en.wikipedia.org/wiki/Square_rootedit: One thing I dont understand is why everyone is saying that 'if n is positive, sqrt of n is obviously positive'.....the only thing that can be said if m is positive is that sqrt of n is definitely real, (and also that n is not zero so division is possible.) it is true that sqrt of n
will be positive...as explained in the wiki article cited above, but it has got nothing to do with thefact that n is positive.
Quote:
In this question , since we're given that both m and n are positive, we can conclusively say that the outcome will be positive 10
ok...so m is positive, but sqrt of n could still have been negative....and made the term (m)(sqrt n)= -10
Please , can someone please tell me, am I missing something here?