ruplun wrote:In GMAT , is sqaure root of a integer is considered positive always? and if x^2 = 9y^2 , what is the value of x , please do let me know

You are right, the sqaure root of an integer is considered positive.

The above post is not correct; a positive number has two square roots. The square roots of 4 are 2 and -2, because 2^2 and (-2)^2 are both equal to 4. However, when you see the 'square root symbol' (√), by definition that produces only the non-negative square root of what is underneath. So if you see something like √4, that is equal to 2 (and never to -2).

You might look at pg. 114 of OG12 ('every positive number n has two square roots, one positive and the other negative, but √n denotes the positive number whose square is n').