Ans: A
$\begin{array}{cl}
& pr+qr -ps-qs \\
= & r(p+q) -s(p+q) \\
= & (p+q)(r-s)
\end{array}$
$\begin{array}{cl}
& pr+qr -ps-qs \\
= & r(p+q) -s(p+q) \\
= & (p+q)(r-s)
\end{array}$
Resources for HKDSE Mathematics
Resources for HKDSE Mathematics
