(1)等比数列｛an},首项为81设an=a1*q^(n-1)=81*q^(n-1)数列{bn}满足bn=log3为底an∴bn=log3为底[81*q^(n-1)]=log3为底81+log3为底q^(n-1)=4+(n-1)log3为底q=log3为底q*n+4-log3为底q∵log3为底q为常数,∴bn为以4为首...