question_answer

If x + y varies directly with x - y, then which one of the following is true?

A) x and y vary directly  

B) \[{{x}^{2}}+\text{ }{{y}^{2}}\] and \[{{x}^{2}}-\text{ }{{y}^{2}}\] vary directly

C) Both A and B

D) \[{{x}^{2}}+\text{ }{{y}^{2}}\] and \[{{x}^{2}}-\text{ }{{y}^{2}}\] vary indirectly

E) None of these