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msbroker: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Tue Dec 08, 2009 11:08 am

by msbroker » Tue Mar 02, 2010 4:28 pm

Is it true that x > 0?

(1) x^2 = 2x
(2) x^3 = 3x

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Source: Beat The GMAT — Data Sufficiency | Tue Mar 02, 2010 4:28 pm

dmateer25: Community Manager; Posts: 1049; Joined: Sun Apr 06, 2008 5:15 pmFollowed by: 27 members; Location: Pittsburgh, PA; Thanked: 113 times; GMAT Score:710

by dmateer25 » Tue Mar 02, 2010 4:34 pm

1)
x^2 = 2x
x^2 - 2x = 0
x(x-2)=0
x=0 or x=2
Not Suff

2)
x^3 = 3x
x^3 - 3x = 0
x(x + sqrt3)(x - sqrt3) = 0
x=0 or x=-sqrt3 or x=sqrt3
Not suff

Together the only common result is 0 so 1 and 2 together are SUFF

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msbroker: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Tue Dec 08, 2009 11:08 am

by msbroker » Tue Mar 02, 2010 4:45 pm

thanks dmateer...just to elaborate on this question, the OA explanation contains a typo for (2) it says:

(2) if x^3 = 3x, then x^3 - 3x = 0. This can be solved by factoring this equation x^2(x-3) = 0. ...so x^2 = 0 and x-3 = 0 giving 0 and 3 as the answer....

Either way you get the same answer (0 is the only commong factor btw the two), but you would think the money GMAC makes you fork over for GMATfocus they would at least not have any typos. Thanks

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