1/2 7/9 13/16 19/13 5/6 ( )A．10/11 B．11/12 c．31/37 D．33/37
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我猜测题有印刷错误,应是:1/2 7/9 13/16 19/23 5/6 ( )A．10/11 B．11/12 c．31/37 D．33/37 答案是31/37.理由:1/2 ,7/9 ,13/16 ,19/23 ,25/30 ,31/37,.....An=(6n-5)/(7n-5)分子和分母各为一等差数列,
1/2 7/9 13/16 19/13 5/6 ( )A．10/11 B．11/12 c．31/37 D．33/37
我猜测题有印刷错误,应是:1/2 7/9 13/16 19/23 5/6 ( )A．10/11 B．11/12 c．31/37 D．33/37 答案是31/37.理由:1/2 ,7/9 ,13/16 ,19/23 ,25/30 ,31/37,.....An=(6n-5)/(7n-5)分子和分母各为一等差数列,