2014-II-13

16-06-2021 app.cch No Comments

Ans: C
Let

z = \frac{k y^{3}}{x}

, where

k

is a non-zero constant. Then, we have

$\begin{array}{rcl} z & = & \frac{k y^{3}}{x} \\ k & = & \frac{x z}{y^{3}} \\ \frac{1}{k} & = & \frac{y^{3}}{x z} \end{array}$

Therefore, $\frac{y^{3}}{x z}$ must be constant.

2014, HKDSE-MATH, Paper 2 Variations