For all numbers l and m, the operation @ is defined by l@m = l^2 - lm. If xy ≠ 0, then which of the following can be equal to zero?
I. x@y
II. (xy)@y
III. x@(x + y)  Choose the correct choice.
A) II  B) I and II  C) I and III  D) II and III  E) All of the above
l@m= l^2 - lm=l(l-m).... so l@m will be zero if l=m or l=0.. but a cannot be equal to 0.. as per Q, x and y can take any int value except 0...   now lets look at the choices..   when x=y, it will be 0... so ok...   when we put xy=y, it is possible when x=1 and y any integer... so ok again   when we put x=x+y.... only possibility when y=0 and it is given x and y cannot be 0....so not possible   only l and ll possible   answer: I and II
<result>B</result>
For all numbers l and m, the operation @ is defined by l@m = l^2 - lm. If xy ≠ 0, then which of the following can be equal to zero?
I. x@y
II. (xy)@y
III. x@(x + y)