如图
=(2²-1²)+(4²-3²)+……+(100²-99²)
=3+7+……+199
=(3+199)*50/2
=5050
=(2²-1²)+(4²-3²)+(6²-5²)+……+(98²-97²)+(100²-99²)
=(2-1)(2+1)+(4-3)(4+3)+(6-5)(6+5)+……+(98-97)(98+97)+(100-99)(100+99)
=(2+1)+(4+3)+(6+5)+……+(98+97)+(100+99)
=(1+2)+(3+4)+(5+6)+……+(97+98)+(99+100)
=1+2+3+4+5+6+……+97+98+99+100
=(1+100)×100÷2
=101×50
=5050