Question

数列{an}中,a1=2,an+1=4an-3n+1,求证{an-n}是等比数列 4an中n为下标an+1中n+1为下标

Answer 1

a[n+1]-(n+1)=4a[n]-3n+1-(n+1)=4a[n]-4n=4(a[n]-n)

所以a[n+1]-(n+1)/(a[n]-n)=4

即{a[n]-n}等比

中括号为下标