Graph coordinate system - gmat prep

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Graph coordinate system - gmat prep

by mjjking » Mon Apr 06, 2009 6:06 am
OA is C .
Please forgive me if this question has been posted already!
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Source: — Data Sufficiency |

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by sacx » Mon Apr 06, 2009 6:24 am
y = (x+a)(x+b)
y = x^2 + (a+b)x +ab

stmt I

a+b = -1

y = x^2 -x +ab

we cannot solve the equation

Insufficient

Stmt II

point of intersection (0.-6)

-6 = ab

Insufficient

Stmt I & II

y = x^2 -x - 6

for the graph to intersect at x-axis, y = 0

0 = x^2 -x - 6

x = 3,-2

[spoiler]Sufficient

C[/spoiler]
SACX

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by mjjking » Mon Apr 06, 2009 10:27 pm
why you get that ab is -6? Sorry I don't get this :)
Beat The GMAT - 1st priority
Enter a top MBA program - 2nd priority
Loving my wife: MOST IMPORTANT OF ALL!

REAL THING 1 (AUG 2007): 680 (Q43, V40)
REAL THING 2 (APR 2009): 720 (Q47, V41)

Master | Next Rank: 500 Posts
Posts: 139
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Thanked: 17 times

by sacx » Mon Apr 06, 2009 10:50 pm
by substituting x = 0 and y = -6 in the equation y = x^2 + (a+b)x +ab
SACX