DS +ve/-ve cases with square and power 4 from Advanced GMAT

[pssundeep]

I am solving a DS problem on page 106 from the Manhattan Advanced GMAT Quant book. The solution claims that "a" must be positive if "a² = b²". How about this situation ?

a = -2
b = 2
Then a² = b².

What is the reasoning behind the conclusion "b² is positive, so 'a' is positive." on page 107.

[tim]

My version of the book says a = b^2, not a^2 = b^2. Are you sure yours has an a^2? If so, this must have been one of the mistakes that got corrected in the latest version of the book.

[pssundeep]

Thank you for the quick reply ! Yes, i am sure that my version has
a² = b². I have that page open in front of me right now.

Good to know that it has been fixed in later versions of the book. It won't leave the students puzzled :)

My book details:
------------------
Year: 2012
10 Digit Book number: 1-935707-15-9

Thanks again !

[tim]

FYI you can also look up any suspected typos (or alert us to new ones) at http://www.manhattangmat.com/errata.cfm