如何简便计算1-2+3-4+5-6+------+99-100

1-2+3-4+5-6+------+99-100

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

=-1+ -1 + -1 +-1 +………… +-1

=-50 yi一共有50个 -1

1-2+3-4+5-6+------+99-100
=(1-2)+(3-4)+(5-6)+------+(99-100)
=-1-1-1....-1
=-50

1-2=-1 3-4=-1 5-6=-1…共有50对所以等于-50

用1+99=100 然后-2-98=-100
这样一对对的消 就行了