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一百加99减98加97减96加95减94加……八加七减六加五...

100+99-98+97-96+......+5-4+3-2 =100+(99-98)+(97-96)+......+(5-4)+(3-2) =100+1X49 =149

就是101+99-98-97+96+95-94-93吗?后面没有数了?

1+2-3+4+5-6+……+97+98-99+100 =(1+2-3)+(4+5-6)+……+(97+98-99)+100 =0+3+……+96+100 =(0+96)×33÷2+100 =1584+100 =1684

100-98+96-94+92-……+8-6+4-2 =2+2+2+……+2+2 =2X49=98 或(100+96+92+……+4)-(98+94+90+……+2) =(100+4)X49/2-(98+2)X49/2 =52X49-50X49 =49(52-50) =98

100²-99²+98²-97²+96²-95²+……+2²-1² =(100+99)×(10-99)+(98+97)×(98-97)+(96+95)×(96-95)+……+(2+1)×2-1) =100+99+98+97+96+95+……+2+1 =(100+1)×100÷2 -5050

。。。0

原式=(1-2)+(3-4)+...+(99-100) =(-1)×50 =-50 供参考

100+99-98-97+96+95+...+8+7-6-5+4+3-2-1 =(100-98)+(99-97)+...+(8-6)+(7-5)+(4-2)+(3-1) =2+2+...+2+2+2+2 =2×50 =100

减肥

1-2+3-4+5-6+99-100 =(1-2)+(3-4)+(5-6)+(99-100) =(-1)+(-1)+(-1)+(-1) =-4

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