等差數(shù)列公式

第n項(xiàng)的值，an=首項(xiàng)+(項(xiàng)數(shù)-1)×公差

前n項(xiàng)的和，Sn=首項(xiàng)×n+項(xiàng)數(shù)(項(xiàng)數(shù)-1)公差/2

公差d=(an-a1)÷(n-1)(其中n大于或等于2，n屬于正整數(shù))

項(xiàng)數(shù)=(末項(xiàng)-首項(xiàng))÷公差+1

末項(xiàng)=首項(xiàng)+(項(xiàng)數(shù)-1)×公差

當(dāng)數(shù)列為奇數(shù)項(xiàng)時，前n項(xiàng)的和=中間項(xiàng)×項(xiàng)數(shù)

數(shù)列為偶數(shù)項(xiàng)，前n項(xiàng)的和=(首尾項(xiàng)相加×項(xiàng)數(shù))÷2

等差數(shù)列中項(xiàng)公式2an+1=an+an+2其中{an}是等差數(shù)列

等差數(shù)列的和=(首項(xiàng)+末項(xiàng))×項(xiàng)數(shù)÷2。