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gmat prep functions

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Senior | Next Rank: 100 Posts
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gmat prep functions

by [email protected] » Tue Aug 12, 2008 6:56 am
I managed to figure out 1 and 2 easily and guessed the answer right but on review I am struggling to see how to work out 3, can someone give me hand please?

Thanks
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by santa_dem » Tue Aug 12, 2008 7:05 am
Open those brackets:

(a+b-ab)*c=ac+bc+abc

a*(b+c-bc)=ab+ac+abc

(1) and (2) are not always true, so it leaves us to I and II.
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by [email protected] » Tue Aug 12, 2008 7:10 am
The OA is E so I,II and III must all be true?
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by santa_dem » Tue Aug 12, 2008 7:20 am
wow... sorry.

Totally lost it.

Here goes:

Open those brackets:

(a+b-ab)@c=(a+b-ab)+c-(a+b-ab)*c=a+b-ab+c-ac-bc+abc=

a+b+c+abc-ab-bc-ac

a@(b+c-bc)=a+(b+c-bc)-a*(b+c-bc)=a+b+c-bc-ab-ac+abc=
a+b+c+abc-ab-bc-ac

So all I,II and III are true
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