问题
填空题
如果数列{an}满足a1=3,an-an+1=5anan+1(n∈N*),则an=______.
答案
将an-an+1=5anan+1两边同除以anan+1 得
-1 an+1
=5,1 an
∴数列{
}是等差数列,1 an
=1 an
+(n-1)×5=1 3
,15n-14 3
an=3 15n-14
故答案为:3 15n-14
如果数列{an}满足a1=3,an-an+1=5anan+1(n∈N*),则an=______.
将an-an+1=5anan+1两边同除以anan+1 得
-1 an+1
=5,1 an
∴数列{
}是等差数列,1 an
=1 an
+(n-1)×5=1 3
,15n-14 3
an=3 15n-14
故答案为:3 15n-14