Data Sufficiency

If a data sufficiency Q asks: What is the value of integer x? and one of the statement stems (say statement stem 2) has a quadratic equation which yields two values for x (both integers); then on that basis can statement 2 be said to be insufficient on its own?

To me it seems the "value" of x (though expressed in singular) should be considered to be satisfied even if a quadratic equation is involved which yields two integer values... But Bin 3, "Cracking the GMAT 2010 edition", Q. 26 reasons otherwise and considers statement 2 insufficient. Is this the way to go on the GMAT? Thanks!

No you're wrong. The question asks for a single value of x and you must strictly get only 1 value of x. If you don't, then it should be considered insufficient.

To quote the Official Guide (and the directions that you see on test day):

Note: In data sufficiency problems that ask for the value of a quantity, the data given in the statements are sufficient only when it is possible to determine exactly one numerical value for the quantity.

Ooops --- better read the instructions carefully! Thanks!

There is, however, one exception to this rule. If you're looking for a value that, by definition, could only be positive, and the quadratic equation is such that it yields one positive and negative solution, it will still be sufficient.

For example, if you're looking for the side of a rectangle, x, and the statement tells you something like "x^2 = 4" then it's sufficient since you can never have a negative length.

Stuart Kovinsky wrote:To quote the Official Guide (and the directions that you see on test day):

Note: In data sufficiency problems that ask for the value of a quantity, the data given in the statements are sufficient only when it is possible to determine exactly one numerical value for the quantity.