巧算下面的算式.1+3+5+7+……+29-2-4-6-……-28

2024-10-31 20:21:46
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1+3+5+7+……+29-2-4-6-……-28
=(1-2)+(3-4)+.+(27-28)+29
=(-1)x14+29
=29-14
=15