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Source: — Data Sufficiency |
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by rijul007 » Sun Feb 12, 2012 11:29 am
queenisabella wrote:Data Sufficiency

In the xy-plane, at what two points does the graph of y=(x+a)(x+b) intersect the x-axis?
(1) a+b=-1
(2) The graph intersects the y-axis at (0,-6).
y = x^2 +x(a+b) +ab

we need values of x for
x^2 + x(a+b)+ab = 0

(1) a+b=-1
x^2 -x +ab = 0

Insuff

(2) The graph intersects the y-axis at (0,-6).

-6 = (0+a)(0+b)
ab = -6

x^2 +x(a+b)-6=0

Insuff

Combining the two sts

x^2 -x -6 = 0
(x+2)(x-3)=0

(-2,0) and (3,0)


IMO : OPTION C
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