(-1)+2+(-3)+4+……+(-99)+100 (-1)+2+(-3)+4+……+(-99)+100
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![(-1)+2+(-3)+4+……+(-99)+100 (-1)+2+(-3)+4+……+(-99)+100](/uploads/image/z/13373890-34-0.jpg?t=%28-1%29%2B2%2B%28-3%29%2B4%2B%E2%80%A6%E2%80%A6%2B%28-99%29%2B100+%28-1%29%2B2%2B%28-3%29%2B4%2B%E2%80%A6%E2%80%A6%2B%28-99%29%2B100)
(-1)+2+(-3)+4+……+(-99)+100 (-1)+2+(-3)+4+……+(-99)+100
(-1)+2+(-3)+4+……+(-99)+100
(-1)+2+(-3)+4+……+(-99)+100
(-1)+2+(-3)+4+……+(-99)+100 (-1)+2+(-3)+4+……+(-99)+100
(-1)+2+(-3)+4+省略号+(-99)+100
=(2-1)+(4-3)省略号+(100-99)
=1*50
=50
(-1)+2=1 (-3)+4=1 ...(-99)+100=1 共50个1 所以
(-1)+2+(-3)+4+……+(-99)+100=50
你也可以把这题目看成2个等差数列一个递增的 2 , 4 ...100 =50*2+50(50-1)*2/2
=50*51 一个递减的等差数列 (-1) , (-3)...(-99)=50*(-...
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(-1)+2=1 (-3)+4=1 ...(-99)+100=1 共50个1 所以
(-1)+2+(-3)+4+……+(-99)+100=50
你也可以把这题目看成2个等差数列一个递增的 2 , 4 ...100 =50*2+50(50-1)*2/2
=50*51 一个递减的等差数列 (-1) , (-3)...(-99)=50*(-1)+50*(50-1)*(-2)/2=50*(-50)
所以=50*51+50*(-50)=50
收起
(-1)+2+(-3)+4+省略号+(-99)+100
=(2-1)+(4-3)省略号+(100-99)
=1*50
=50