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Junior | Next Rank: 30 Posts
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GMAT Prep Question

by mindruna » Sat Aug 04, 2007 11:19 am
In the xy plane, at what 2 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)

I guessed E, but the OA is C. How?

Thanks!
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Source: — Data Sufficiency |
Junior | Next Rank: 30 Posts
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by karthick451 » Sat Aug 04, 2007 11:08 pm
y = x^2 + ax +bx + ab

intercepts x axis when y = 0

essentially need to solve the quadratic

x^2 + ax +bx + ab = 0

statement 1 gives value of a+b
statement 2 gives value of ab

and hence with both the statement the equation can be solved.
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