文档介绍：数学必修5· (1)等差数列{an},对于任意正整数n,都有an+1-an=________.(2)等差数列{an},对于任意正整数n、m,都有an-am=.(1)想一想:在等差数列{an}中,若已知任意两项am,an,怎样求公差?(2)观察下列数列:①-5,-3,-1,1,3,5,7;②120,117,114,111,108,:在有穷等差数列中,与首末两项“等距离”的两项之和有何特点?d(n-m)d(3)设数列{an}的通项为an=3n-2,计算a1+a5,a2+a4,a11+a23,a15+a19,a17,你发现了什么?{an}的一些简单性质(1)对于任意正整数n、m都有an-am=(n-m)d.(2)对任意正整数p、q、r、s,若p+q=r+s,则ap+aq=ar+、q、r若p+q=2r,则ap+aq=________.(3)对于任意非零常数b,若数列{an}成等差,公差为d,则{ban}也成等差数列,(4)若{an}与{bn}=an+bn,dn=an-},{dn}都是等差数列.(5)等差数列{an},a4,a7,…,a3n-2,…{an}的公差为d,则当d=0时,等差数列{an}是常数列,当d<0时,等差数列{an}是单调递_______数列;当d>0时,等差数列{an}-1