From 75a5c861e984283f4c7b59f5ef3719d4103b0cc1 Mon Sep 17 00:00:00 2001 From: Zhao Xin <7176466@qq.com> Date: Wed, 7 Sep 2022 21:40:33 +0800 Subject: [PATCH] gitpush --- 问题/等差数列.md | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/问题/等差数列.md b/问题/等差数列.md index c4df8d5..710b57d 100644 --- a/问题/等差数列.md +++ b/问题/等差数列.md @@ -9,12 +9,10 @@ $$ a_n = a + (n-1)d \tag{等差数列通项公式} $$ -换句话说,任意一个等差数列 $\{a_{n}\}$ 都可以写成:$\{\,a,\,a+d,\,a+2d,\,\cdots,\,a+(n-1)d\,\}$ - 由等差数列通项公式可以得到以下公式: $$ n = \dfrac{a_n - a}{d} + 1 \tag{已知首项尾项及公差求项数}$$ -等差数列求和公式: +换句话说,任意一个等差数列 $\{a_{n}\}$ 都可以写成:$\{\,a,\,a+d,\,a+2d,\,\cdots,\,a+(n-1)d\,\}$ -$$ \dfrac {(a + a_n) \times n}{2} $$ +$$ 等差数列各项的和 = \dfrac {(a + a_n) \times n}{2} $$