lucyqin wrote:

Can someone please explain to me again why square root of 4 cannot be -2 as well as 2? Is it the square root of a number always have two roots, one positive and one negative?

True, by definition, square roots have a positive and negative value, but the GMAT only recognizes the positive root of a number.

Example: root4 = +2 (not -2)

However, if you are squaring a variable, the value for that variable will be a positive and negative value

Example: x^2 = 4 --> x = +/-2

Just something to keep in mind on test day!!

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Factorials were someone's attempt to make math look exciting!!!