(9n^2-9n+2)/(9n^2-1)=(9n^2-1-9n+3)/(9n^2-1)=1-3(3n-1)/(3n-1)(3n+1)=1-3/(3n+1)
n≥1
1/4≤1-3/(3n+1)<1
各项都在区间(0,1)上
1/3<1-3/(3n+1)<2/3
7/6
(9n^2-9n+2)/(9n^2-1)=(9n^2-1-9n+3)/(9n^2-1)=1-3(3n-1)/(3n-1)(3n+1)=1-3/(3n+1)
n≥1
1/4≤1-3/(3n+1)<1
各项都在区间(0,1)上
1/3<1-3/(3n+1)<2/3
7/6