2008-II-03

21-06-2023 app.cch 尚無留言

答案：A

\begin{array}{rcl} \frac{- k}{1 - k} - \frac{1}{k - 1} & = & \frac{- k}{- (k - 1)} - \frac{1}{k - 1} \\ = & \frac{k}{k - 1} - \frac{1}{k - 1} \\ = & \frac{k - 1}{k - 1} \\ = & 1 \end{array}