设数列{an}{bn}均为等差数列,公差都不为0,无穷数列liman/bn=3,则无穷数列limb1+b2+...+bn/na3n=

问题描述:

设数列{an}{bn}均为等差数列,公差都不为0,无穷数列liman/bn=3,则无穷数列limb1+b2+...+bn/na3n=
..那个那个.....

an=a1+(n-1)m
bn=b1+(n-1)p
则liman/bn=m/p=3
1im(b1+b2+...+bn)/n*a3n=lim(nb1+n(n-1)p/2)/n*(a1+(3n-1)m)=p/6m=1/18