Roots (numbers versus variables)

[kim0928]

***Reposted to Correct Folder with Follow up Question***

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Joined: Tue Jun 09, 2015 10:32 am

Roots (numbers versus variables)

Thu Aug 27, 2015 5:51 pm

In Guide 2: Algebra (pg. 71), the direction is "If a given equation contains a square root symbol on the GMAT, only use the positive root. If an equation contains a squared variable, and you take the square root, use both the positive and negative solutions." This make sense. Then, in the solutions to Chapter 5, there is a note that says "On the GMAT, when given a square root symbol with a number beneath, you are supposed to take only the positive root. This restriction does not apply when given exponents." Does the original rule apply only to number for the GMAT (versus variables)?

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tim
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Re: Roots (numbers versus variables)

Fri Aug 28, 2015 8:46 am

The distinction lies entirely in whether the GMAT provided the square root sign (take only the positive value) or you drew the square root sign in yourself (take both positive and negative values). Does this clear up your concern? If not, please describe in more detail what the issue is and we'll be glad to help further.

***Follow Up Question***

Thank you, Tim. Does this rule also apply to variables beneath the square root sign (i.e If the GMAT provides a square root sign over a variable, take only the positive value?).

[tim]

Yes it does.

[RonPurewal]

this is also the kind of thing you could figure out by yourself—just by thinking about what would ensue if the '√' symbol really were ambiguous.

consider:
you have a square whose sides are each 1 unit long. how many units long is the diagonal?
you'll write... '√2'
...and, right there, we have the reason why the '√' symbol only means one thing.

•••IF••• '√2' could mean either a positive or a negative value, then...
...no one would know which value you meant,
and
...it would become IMPOSSIBLE to write the answer to the question above—unless you invented another symbol to mean the positive root.
woops.

--

also, more generally, mathematical symbols are NEVER ambiguous.
...because that's the reason why mathematical symbols exist in the first place.

[tim]

also, more generally, mathematical symbols are NEVER ambiguous.
...because that's the reason why mathematical symbols exist in the first place.

Where's the "like" button?