回復 15# weiye 的帖子
找想算出通項,可是卻萛不出(k−1)(−1)n+(k−1)n,可否麻煩老師幫我看看那裏算錯了.謝謝‧
an+an−1=k(k−1)n−1
kan=−kan−1+(k−1)n−1
令bn=kan，則bn=−bn−1+(k−1)n−1
bn+1−k(k−1)n=−[bn−1+1−k(k−1)n−1]
bn+1−k(k−1)n=[b1+1−k(k−1)](−1)n−1，而bn=1
bn=k1(k−1)n+[1+1−k(k−1)](−1)n−1=k1(k−1)n+k1(−1)n−1=k1[(k−1)n+(−1)n−1]
an=kbn=(k−1)n+(−1)n−1
