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xy coordinate plane DS Q

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xy coordinate plane DS Q

by tj123 » Sat Dec 13, 2008 7:16 pm
In the XY-coordinate plane, line l and k intersect at the 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


The answer is c) Both

Please explain.
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Source: — Data Sufficiency |
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by ravikirancheni » Sun Dec 14, 2008 2:49 am
Let the two lines be

Y = Mx + C --- 1
Y = Ax + B --- 2

So Slope of line 1 is M , Line 2 is A.
X intercepts being -C/M , -B/A

Product of slopes --> MA.

ST-1

the product of the x intercepts of lines l and k is positive
i,e CB/MA is -ve.

Nothing can be derived

ST-2

the product of the y-intercepts of lines l and k is negative
i,e CB is -ve nothing can be derived


ST-1,ST-2

combining both MA has to be -ve ...

So that is we are ought to check

Ans; C

Keep rockin !
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by amgbeano » Wed Sep 01, 2010 5:32 am
I assume you meant to say that MA is +ve.
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