Problem: Indicate in which one of the following equations yyy is neither directly nor inversely proportional to xxx:
Answer Choices:
A. x+y=0x+y=0x+y=0
B. 3xy=103 x y=103xy=10
C. x=5yx=5 yx=5y
D. 3x+y=103 x+y=103x+y=10
E. xy=3\dfrac{x}{y}=\sqrt{3}yx​=3​ Solution:
(A), (B), (C), and (E) are of the form y=kxy=k xy=kx or xy=kx y=kxy=k, but (D) is not.