求和、首項(xiàng)、末項(xiàng)等

熱心網(wǎng)友

等比數(shù)列：a,aq,aq^2,aq^3,…,aq^(n-1),…首項(xiàng)a，通項(xiàng)an=aq^(n-1),前n項(xiàng)部分和Sn=[a(1-q^n)]/(1-q)當(dāng)|q|<1時(shí)，等比數(shù)列的和S=a/(1-q).數(shù)列一般是沒(méi)有末項(xiàng)的.