(-1)+(+2)+(-3)+(+4)+...+(-99)+(+100)怎么算
问题描述:
(-1)+(+2)+(-3)+(+4)+...+(-99)+(+100)怎么算
答
(-1)+(+2)+(-3)+(+4)+...+(-99)+(+100)=
(2+4+6...+100)-(1+3+5.+99)=
50*(2+100)/2-50*(1+99)/2=25*(2+100-100)=50