等差数列{an}与{bn}
等差数列{an}与{bn},它们的前n项之和分别为Sn与Sn',如果Sn/Sn'=7n+1/4n+2等差数列{an}与{bn},它们的前n项之和分别为Sn与Sn',如果Sn/Sn'=7n+1/4n+27,则a11/b11=
等差数列{an}与{bn},它们的前n项之和分别为Sn与Sn',如果Sn/Sn'=7n+1/4n+27,则a11/b11= 解:a11/b11= 2a11/2b11= (a1+a21)/(b1+b21)= n(a1+a21)/n(b1+b21)= [n(a1+a21)/2]/[n(b1+b21)/2]= S21/S21'= (7*21+1)/(4*21+27)= 148/111= 4/3
答:等差数列的一个性质:m+n=p+q--->am+an=ap+aq a100/b100=2a100/(2b100) =(a1+a199)/(b1+b100) =[...详情>>
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