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奇數(shù)項和：S奇 = [a(a 2nd)](n 1)/2 = (a nd)(n 1)，偶數(shù)項和：S偶 = [(a d)(a 2nd-d)]n/2 = (a nd)n 。

奇數(shù)項和偶數(shù)項和公式數(shù)列奇數(shù)項偶數(shù)項求和

什么是等差數(shù)列
等差數(shù)列指的是從第二項起，每一項與它的前一項的差等于同一個常數(shù)的一種數(shù)列，常用A、P表示。這個常數(shù)叫做等差數(shù)列的公差，公差常用字母d表示。

奇數(shù)項和偶數(shù)項的求和公式
奇數(shù)項為：a，dua 2d，a 4d，.............，a 2nd
【奇數(shù)項和偶數(shù)項和公式數(shù)列奇數(shù)項偶數(shù)項求和】奇數(shù)項和：S奇 = [a(a 2nd)](n 1)/2 = (a nd)(n 1)
偶數(shù)項為：a d，a 3d，a 5d，.............，a (2n-1)d
偶數(shù)項和：S偶 = [(a d)(a 2nd-d)]n/2 = (a nd)n