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GMAT prep coordinate geometry

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GMAT prep coordinate geometry

by awilhelm » Tue Jan 20, 2009 2:15 pm
In the xy-coordinate plane, line L and line K intersect at point (4,3). Is the product of their slopes negative?

1) The product of the x-intercepts of lines L and K is positive.
2) The product of the y-intercepts of lines L and K is negative.
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by amitabhprasad » Tue Jan 20, 2009 4:25 pm
I am getting "E" whats OA
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by awilhelm » Tue Jan 20, 2009 6:25 pm
OA is C. Hmmm...
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by hypik21 » Tue Jan 20, 2009 10:35 pm
its best to draw a graph...

statement 1...if the product of x ints are neg, each one indiv. is either negative or positive....you can draw positive and negative sloping lines through 4,3 with both negative and positive x intercepts..

statement 2....one of the y intercepts will be neg, one will be positive..you can draw 2 positive sloping lines through 4,3 or 1 negative sloping line and 1 positive sloping line..inuf

if you take both statements together, there will be one line that will have a positive y and x intercept..this line has to have a negative slope..there is no way to draw a positive sloping line through 2 negative intercepts/positive intercepts...the other line must be positive since it has one negative and one positive intercept

C
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by amitabhprasad » Tue Jan 20, 2009 10:53 pm
Thanks hypik21,
It was poor reading from my part.
I read "product of their slopes negative" as product of slope is "-1" so was looking if the two lines are perpendicular.
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by awilhelm » Wed Jan 21, 2009 8:40 am
Correct, thanks for the explanation!
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