2017-I-08

16-06-2021 app.cch No Comments

Ans: (a)

y = \frac{972}{\sqrt{x}}

(b)

27

Let $y = \frac{k}{\sqrt{x}}$ , where $k$ is a non-zero constant.
When $x = 144$ , $y = 81$ . We have

$\begin{array}{rcl} 81 & = & \frac{k}{\sqrt{144}} \\ 81 & = & \frac{k}{12} \\ k & = & 972 \end{array}$

Therefore, $y = \frac{972}{\sqrt{x}}$ .
Sub. $x = 324$ into the equation found in (a), we have
$\begin{array}{rcl} y & = & \frac{972}{\sqrt{324}} \\ = & 54 \end{array}$

Hence, the change in the value of $y$

$\begin{array}{cl} = & 81 - 54 \\ = & 27 \end{array}$

2017, HKDSE-MATH, Paper 1 Variations

Leave a Reply Cancel reply