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Difference between different types of brackets used

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by DanaJ » Thu Sep 03, 2009 5:40 am
If you have a square bracket, the interval also contains the "head" of the interval. If it's just a round bracket, then that head is not included.
In your examples:

[0,5] means 0 <= x <=5

(0,5) means 0 < x < 5

[0,5) means 0 <= x < 5
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by winnerhere » Thu Sep 03, 2009 7:20 am
Thanks danaj :)

what abt {}
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by Ian Stewart » Thu Sep 03, 2009 2:21 pm
Dana's explanation is perfect, but I've never seen a real GMAT question which uses that notation for an interval (ranges of values are always expressed using inequalities, a number line, or words), so you likely don't need to know it. In algebra, square brackets [] and parentheses () have the same meaning (in algebra texts, you'll sometimes see square brackets used as outer brackets when there are brackets within brackets), though I don't think I've ever seen that on the GMAT either - I'm pretty sure the GMAT uses standard parentheses exclusively in algebraic expressions. Set braces {} will only be used in a question about sets, so if you see something like {6}, that's the one element set containing the number 6.
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by DanaJ » Thu Sep 03, 2009 10:11 pm
On top of what Ian said, we also have this notation in Romania:

{2.34} = 0.34
{3} = 0

We call this the "fractional part" of a number. However, seeing this on the GMAT is impossible, since I understand it is a pretty specific notation.
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