Hi all,
Would love to hear an expert’s opinion but all are welcome.
If xy>0, does (x-1)(y-1) = 1
1. x+y = xy
2. x=y
we can obviously conclude that 1. Is sufficient by re-writing the problem
xy-x-y+1=1……..which is the same as 1.
However, I would like to see where my thinking is wrong for the 2nd one because I concluded that it was sufficient.
If x=y, then
(y-1)(y-1)=1
Y^2-2y=0
Y(y-2)=0
Either y=0 or y=2.
Now, the stem mentions that xy>0, thus y cannot be 0, thus y=2
(x-1) (2-1)=1
(x-1)=1
x=2
We know both x & y and thus can solve the problem.
The OG explanation stops at y^2-2y=0, but can we not continue?
Would love to hear your opinion, thanks!
Would love to hear an expert’s opinion but all are welcome.
If xy>0, does (x-1)(y-1) = 1
1. x+y = xy
2. x=y
we can obviously conclude that 1. Is sufficient by re-writing the problem
xy-x-y+1=1……..which is the same as 1.
However, I would like to see where my thinking is wrong for the 2nd one because I concluded that it was sufficient.
If x=y, then
(y-1)(y-1)=1
Y^2-2y=0
Y(y-2)=0
Either y=0 or y=2.
Now, the stem mentions that xy>0, thus y cannot be 0, thus y=2
(x-1) (2-1)=1
(x-1)=1
x=2
We know both x & y and thus can solve the problem.
The OG explanation stops at y^2-2y=0, but can we not continue?
Would love to hear your opinion, thanks!
