(1) çæ¯æ°åï¼a (n+1)/an=q (nâN)ã
ãã(2) é项å
¬å¼ï¼an=a1Ãq^(n-1)ï¼
ããæ¨å¹¿å¼ï¼ an=amÃq^(n-m)ï¼
ãã(3) æ±åå
¬å¼ï¼Sn=n*a1 (q=1)
ããSn=a1(1-q^n)/(1-q) =(a1-an*q)/(1-q) (qâ 1)
ãã(q为æ¯å¼ï¼n为项æ°ï¼
ãã(4)æ§è´¨ï¼
ããâ è¥ mãnãpãqâNï¼ä¸mï¼n=pï¼qï¼åam*an=ap*aqï¼
ããâ¡å¨çæ¯æ°åä¸ï¼ä¾æ¬¡æ¯ k项ä¹åä»æçæ¯æ°å.
ããâ¢è¥mãnãqâNï¼ä¸m+n=2qï¼åam*an=aq^2
ãã(5)"Gæ¯aãbççæ¯ä¸é¡¹""G^2=abï¼G â 0ï¼".
ãã(6)å¨çæ¯æ°åä¸ï¼é¦é¡¹a1ä¸å
¬æ¯qé½ä¸ä¸ºé¶.
ãã注æï¼ä¸è¿°å
¬å¼ä¸an表示çæ¯æ°åç第n项ã
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