2008-II-06

21-06-2023 app.cch 尚無留言

答案：C

\begin{array}{rcl} f (4) - f (3) & = & 21 \\ (4)^{2} + k (4) + 7 - [(3)^{2} + k (3) + 7] & = & 21 \\ 16 + 4 k + 7 - 9 - 3 k - 7 & = & 21 \\ k & = & 14 \end{array}