如何计算等差数列中的项数

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有时我们在数学中会遇到这样的问题,需要找出等差数列中的项数。这个问题并不难,按照以下方法就能求出。

  1. How.com.vn 中文: Step 1 找出公差。
    题目中可能会直接给出公差,或者在数列的首或尾给出两个连续的数字。公差用d表示。[1]
  2. How.com.vn 中文: Step 2 找出数列的首项和末项。
    要求出等差数列的项数必须要知道首项和末项。找出后记下来。首项用A表示,末项用L表示。[2]
  3. How.com.vn 中文: Step 3 用下列公式计算项数:项数用n表示。
    公式为:
    n = (L-A)/d + 1
    公式很简单。用末项(L)与首项(A)之差除以公差(d),再加1。[3]
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小提示

  • 末项与首项之差总是能被公差整除。
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警告

  • 不要将首末项之差与公差混淆。
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