求问数学题～～

赵姑娘Cherry · 发表于 2017-4-20 06:17:08

What is the sum of the first four terms of sequence S?(1) After the first two terms of S, the value of each term of S is equal to the average (arithmetic mean) of the last two precedig terms.
(2) The average of the first three terms of S is 10.

条件（2）懂，条件（1）不懂，额。。。句子读不懂。。。
答案解析（1）是这样说的：
given that after the first two terms, the value of each term is equal to the average of the last two preceding terms, then the first four terms of the sequence could be 8,12,10,11, which have a sum of 41. however, the first four terms of the sequence could also be 4,16,10 and 13, which have a sum of 43; not ssss.

哪个value = average of last two?

nixiaoming · 发表于 2017-4-20 11:34:07

我觉得是从第三项开始，每一项都等于前两项的算术平均

赵姑娘Cherry · 发表于 2017-4-21 03:55:47

nixiaoming 发表于 2017-4-20 11:34
我觉得是从第三项开始，每一项都等于前两项的算术平均

谢谢，但是他举例的第四个数挺迷惑的

[原始] 求问数学题～～

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