GMAT Prep 1 DS 19

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GMAT Prep 1 DS 19

by starxx68 » Sun Dec 30, 2007 6:34 pm
In the xy-plane, does the line with equation y = 3x+2 contain the point (r,s)?

(1) (3r+2-s)(4r+9-s)=0
(2) (4r-6-s)(3r+2-s)=0

I got D, but the right answer is C. Can anyone please explain? Thanks!

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by samirpandeyit62 » Sun Dec 30, 2007 8:56 pm
In the xy-plane, does the line with equation y = 3x+2 contain the point (r,s)?

(1) (3r+2-s)(4r+9-s)=0

i.e 3r+ 2 -s =0 or 4r+9-s =0

s =3r+2 or s =4r +9

INSUFF r,s an lie on either of the lines

(2) (4r-6-s)(3r+2-s)=0

4r-6-s =0 i.e s =4r-6
or
3r+2-s =0 i.e 3r+2 =s

INSUFF same as above

Combine s =3r+2 or s =4r +9 & s =4r-6 or 3r+2 =s

now since both the stmts are true s=3r+2 which satisfies both stmts

so s =3r +2 equivalent to y = 3x+2

SUFF

C
Regards
Samir

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by Auzbee » Sun Dec 30, 2007 11:59 pm
Samir you rock !!