原式=(100-99)(100+99)+(98-97)(98+97)+……+(2-1)(2+1)
=1*(100+99)+1*(98+97)+……+1*(2+1)
=100+99+98+97+……+2+2
=(100+1)+(99+2)+……+(51+50)
=101+101+……+101
=101*50
=5050
原式=(100-99)(100+99)+(98-97)(98+97)+……+(2-1)(2+1)
=1*(100+99)+1*(98+97)+……+1*(2+1)
=100+99+98+97+……+2+2
=(100+1)+(99+2)+……+(51+50)
=101+101+……+101
=101*50
=5050