如题所述
S=1+2+3+...+100 (1)
S=100+99+98+...+1 (2)
(1)+(2)
2S =(1+100)+(2+99)+...+(100+1)
=101x100
S=101x50 =5050
1+2+3+...+100 = S =5050
S=100+99+98+...+1 (2)
(1)+(2)
2S =(1+100)+(2+99)+...+(100+1)
=101x100
S=101x50 =5050
1+2+3+...+100 = S =5050
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