2017-I-06

16-06-2021 app.cch No Comments

Ans: (a)

A^{'} = (- 4 - 3)

,

B^{'} = (9, 9)

$A^{'} = (- 4, - 3)$ , $B^{'} = (9, 9)$ .
Consider the slope of $A B$ , we have
$\begin{array}{rcl} m_{A B} & = & \frac{- 9 - 4}{9 - (- 3)} \\ = & \frac{- 13}{12} \end{array}$

Consider the slope of $A^{'} B^{'}$ , we have

$\begin{array}{rcl} m_{A^{'} B^{'}} & = & \frac{9 - (- 3)}{9 - (- 4)} \\ = & \frac{12}{13} \end{array}$

Hence, we have

$\begin{array}{rcl} m_{A B} \times m_{A^{'} B^{'}} & = & \frac{- 13}{12} \times \frac{12}{13} \\ = & - 1 \end{array}$

Therefore, $A B$ is perpendicular to $A^{'} B^{'}$ .

2017, HKDSE-MATH, Paper 1 Coordinates

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