quadratic

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members; Thanked: 32 times

by Gurpinder » Fri Sep 03, 2010 11:28 am

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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Source: Beat The GMAT — Problem Solving | Fri Sep 03, 2010 11:28 am

debmalya_dutta: Master | Next Rank: 500 Posts; Posts: 385; Joined: Sun Jul 12, 2009 10:16 pmFollowed by: 2 members; Thanked: 29 times; GMAT Score:710

by debmalya_dutta » Fri Sep 03, 2010 6:03 pm

Gurpinder wrote:

from the first equation
X= 0 or -1/2
from the 2nd eqn , X = -1/2 or 3/2

[spoiler]common soln is -1/2
Hence B[/spoiler]

@Deb

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rohit_gmat: Master | Next Rank: 500 Posts; Posts: 158; Joined: Wed Jun 16, 2010 8:21 amFollowed by: 1 member; Thanked: 13 times

by rohit_gmat » Fri Sep 03, 2010 11:18 pm

I would plug in the answer choices.

Start off with D, which shows us that x should not be a positive number :
x (2x+1) = 0
if x is positive, we will never get it equal to zero.

So now try picking B (the better of the 2 negative choices), which gives us :
-(1/2) ( 2 (-1/2) +1) = 0
& (-1/2 + 1/2) x (.....) = 0

So the correct answer would be B

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Gurpinder: Legendary Member; Posts: 659; Joined: Mon Dec 14, 2009 8:12 amFollowed by: 3 members; Thanked: 32 times

by Gurpinder » Sat Sep 04, 2010 7:22 am

Thx guys,

you are both right!

"Do not confuse motion and progress. A rocking horse keeps moving but does not make any progress."
- Alfred A. Montapert, Philosopher.

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