若数列{an}是等差数列,an≠0,则【1/a1a2】+【1/a2a3】+`````+【1/a(n-1)an】=?
1.设数列{an}是等差数列,an≠0.求1/a1a2+1/a2a3+...+1/a(n-1)an
已知数列{an},若1/a1a2+1/a2a3+…+1/anan-1=n/anan+1,求证{an}为等差数列.
已知数列an的前n项和是Sn=n^2,则1/a1a2+1/a2a3+...+1/a(n-1)an=?
数列a1=1,an=an+1(1+2an)求证数列an分之一等差数列,若a1a2+a2a3+..+anan+1大于33分
已知数列an满足a1=1,a(n+1)=an/{3(an)+1} Sn=a1a2+a2a3+.+an(an+1),求Sn
已知数列{an}的前n项和Sn=n²+n,求和1/a1a2+1/a2a3+.+1/an-1*an+1/an*a
【急】已知数列an满足1/a1a2+1/a2a3+……1/an-1an=(n-1)/a1an,求证为等差数列
已知数列an为首项a1≠0,公差为d≠0的等差数列,求Sn=1/a1a2+1/a2a3+……+1/ana(n+1)
已知数列an为首项a1≠0,公差为d≠0的等差数列,求Sn=1/a1a2+1/a2a3+……+1/ana(n-1)
{an}为等差数列,an不等于0,d为公差,求证:1/(a1a2)+1/(a2a3)+...+1/(an-1*an)=(
已知数列{an}是等比数列,a2=2,a5=6,则a1a2+a2a3+a3a4+...+ana(n+1)=
等差数列an=2n+3,求和:(1/a1a2)+(1/a2a3)+.+(1/anan+1)