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高中数学选择性必修 第二册(381题)


已知等差数列\(\left\{ {{a_n}} \right\}\)满足\({a_4} = {a_1} + {a_2}\),且\({a_1} \ne 0\),则\(\frac{{{a_5}}}{{{a_1} + {a_3}}} = \)___.



知识点:第四章 数列


参考答案:1


解析:

因为\({a_4} = {a_1} + {a_2}\),所以\({a_1} + 3d = {a_1} + {a_1} + d\),即\({a_1} = 2d\).

因为\({a_1} \ne 0\),则\(d \ne 0\)

所以\(\frac{{{a_5}}}{{{a_1} + {a_3}}} = \frac{{{a_1} + 4d}}{{{a_1} + {a_1} + 2d}} = \frac{{6d}}{{6d}} = 1\).

故答案为:1

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