问题
填空题
在3和一个未知数间填上一个数，使三数成等差数列，若中间项减去6则成等比数列，则此未知数是______．
答案
设此三数为3、a、b，则
，2a=3+b (a-6)2=3b
解得
或a=3 b=3
，a=15 b=27
∴这个未知数为3或27．
故答案为：3或27．
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在3和一个未知数间填上一个数，使三数成等差数列，若中间项减去6则成等比数列，则此未知数是______．
设此三数为3、a、b，则
，2a=3+b (a-6)2=3b
解得
或a=3 b=3
，a=15 b=27
∴这个未知数为3或27．
故答案为：3或27．
| 从方框中选择恰当的词或短语填空.每个只能用一次。 | |
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