GMAT Prep DS

moneyman wrote:Why cant the answer be D ? Both statements give values for r and s and all you need to do is plug in those values in the equation to check if they equal right?

What am I missing here?

what is the OA ?

OA is C..can somebody explain pls?

Hi Maxx,

In this question, we know that if a line passes through a point, the point satisfy the equation of the line.
so, if the line passes through (r,s) this will satisfy the equation.
putting in the original eqn, we get s=3r+2.
so we can rephrase the question as " Is s=3r+2 ?"
from 1.
if you multiply we get a quadratic and we dont get any values.
same with option 2.

but if we combine both 1 and 2.....
and subtract 2 from 1.

check (3r+2 -s) is common in both.
so, final answer is...
(3r+2-s)(4r+9-s-4r+6+s) = 0
(3r+2-s)(15)=0
15 can't be equal to 0, hence 3r+2-s=0 or 3r+2=s which is what we need to prove....
hence ans is C

hope it helps...

jimmiejaz wrote:Hi Maxx,

In this question, we know that if a line passes through a point, the point satisfy the equation of the line.
so, if the line passes through (r,s) this will satisfy the equation.
putting in the original eqn, we get s=3r+2.
so we can rephrase the question as " Is s=3r+2 ?"
from 1.
if you multiply we get a quadratic and we dont get any values.
same with option 2.

but if we combine both 1 and 2.....
and subtract 2 from 1.

check (3r+2 -s) is common in both.
so, final answer is...
(3r+2-s)(4r+9-s-4r+6+s) = 0
(3r+2-s)(15)=0
15 can't be equal to 0, hence 3r+2-s=0 or 3r+2=s which is what we need to prove....
hence ans is C

hope it helps...

Thanks!! For some reason I thought we can both solve each equation for S...