∵點(diǎn)(n,Sn/n)(n屬于N正)均在函數(shù)y=3x-2的圖象上
∴Sn/n = 3n-2 ,即：Sn=3n^2 - 2n
則：S(n-1)=3(n-1)^2 - 2(n-1) =3n^2 - 8n + 5
兩式相減,得：Sn - S(n-1)=6n-5
即：an=6n-5
則a(n+1)=6(n+1)-5=6n+1
bn=3/AnA(n+1) =3/(6n-5)(6n+1)
=3*(1/6)*[1/(6n-5) - 1/(6n+1)]
=(1/2)*[1/(6n-5) - 1/(6n+1)]
則有b1=(1/2)*(1/1 - 1/7)
b2=(1/2)*(1/7 - 1/13)
…
…
bn=(1/2)*[1/(6n-5)-1/(6n+1)]
∴Tn=b1+b2+b3+.+bn
=(1/2)*{(1/1 - 1/7)+(1/7 - 1/13)+.+[1/(6n-5) - 1/(6n+1)]}
=(1/2)*[1-1/(6n+1)]
=3n/(6n+1)