设数列{an}首项为a,公差为d,Sn=[a+(n-1)d]n/2,数列{bn}首项为b,公差为q,Tn=[b+(n-1)q]n/2,Sn/Tn=[a+(n-1)d]/[b+(n-1)q]=5/(2n+4),n=1时,a/b=5/6┄┄①；n=2时,(a+d)/(b+q)=5/8┄┄②；n=3时,(a+2d)/(b+2q)=5/10=1/2...