1-3+5-7+······+97-99= - 知识问答

1-3+5-7+······+97-99=

1个回答

1-3+5-7+······+97-99
=(1-3)+(5-7)+······+(97-99)
=(-2)+(-2)+……+(-2)
=(-2)×[(99+1)÷2]÷2
=(-2)×25
=-50

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