f(n)=1+1/2+1/3+...+1/(3n-1)
f(n+1)=1+1/2+1/3+...+1/(3n-1)+1/3n+1/(3n+1)+
1/(3n+2)
因此
f(n+1)-f(n)=1/3n+1/(3n+1)+1/(3n+2)
此题完毕!
f(n)=1+1/2+1/3+...+1/(3n-1)
f(n+1)=1+1/2+1/3+...+1/(3n-1)+1/3n+1/(3n+1)+
1/(3n+2)
因此
f(n+1)-f(n)=1/3n+1/(3n+1)+1/(3n+2)
此题完毕!