(1²+3²+…+99²)-(2²+4²+…+100²)=?
人气:169 ℃ 时间:2020-01-28 22:03:10
解答
(1²+3²+…+99²)-(2²+4²+…+100²)
=(1+2)×(1-2)+(3+4)×(3-4)+……+(99+100)×(99-100)
=(1+2+3+4+……+99+100)×(-1)
=-(1+100)×100/2
=-5050
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