algebra - multi equations problem from gmat test

[jamulti]

here is a data sufficiency problem:

In the x-y 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 selected D, because 3r + 2 - s = 0 when you input r,s in y=3x+2-> s=3r+2
right answer is C

any ideas?

[Din]

I would go with c.

In 1, either 3r+2-s or 4r+9-s can be zero
In 2, either 4r-6-s or 3r+2-s can be zero
from 1 and 2 (4r+9-s)/(4r-6-s) = 0
=> 4r+9-s = 0
hence r,s is not on the same line.

[sjd00d]

i am always confused with these kind of questions and always screw up. I would have said D too, if the answer was C, would you justify it with the explanation that Din provided or would you actually say that since both statements have s = 3r+2 in common and since that satisfies the equation, the answer to the problem is Yes (and not a definitive NO). Knowing GMAT DS question, 99% of the time the correct answer would have to corroborate the problem statement and not definitively negate it.

[mathphobia]

din. If you have a link or a document that can help me clear my co-ordinate fundas, i'll be glad if you can mail it to me on gulshansaraswat@hotmail.com

[hadi98]

0-0=(3r + 2 - s)(4r + 9 - s)-(4r - 6 - s)(3r + 2 - s) =0
=(3r + 2 - s)[(4r + 9 - s)-(4r - 6 - s)]=0
=(3r + 2 - s)[15]=0
====>(3r + 2 - s)=0
I will go with C

[Din]

Sorry I do not have any. I have followed mostly from various GMAT books recommeded by this forum.

[tibet]

I would have to go with E on this one.

What's the OA?