If xy = – 6, what is the value of xy ( x + y )?
(1) x – y = 5
(2) xy^2= 18
Stmt1. Using xy=-6 and x-y=5, solve for x and y.
You will have 2 set of results
(y=-3, y=-2; x=2, x=3), which result in 2 values: xy(x+y)=6; and xy(x+y)=-6 Hence, insuff.
Stmt2. Again, using xy=-6 and xy^2=18, solve for x and y. You will have 1 set of results
(y=-3; x=2). This results in xy(x+y)=6 Hence, suff.