If |x| = |y| and xy < 0, which of the following must be true?	Choices: A) x+y =-2 B) x+y =-1 C) x+y =0 D) x+y =1 E) x+y =2
1. x and y have same magnitude, |x| = |y|   2. They have opposite signs xy&lt;0   Implies x = -y or y = -x   So x+y =0: x+y =0   Answer x+y =0
<result>C</result>
If |x| = |y| and xy < 0, which of the following must be true?