(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)=

来源：学生作业帮助网编辑：作业帮时间：2024/06/05 03:01:40

(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)=
(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)=

(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)=
(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)
=[(-1)+(+2)]+[(-3)+(+4)]...+[(-41)+(+42)]
=1*42/2
=21

1 2 3 4 1 2 3 4 1 2 3 4 1,2,3,4, 1 2 3 4 1 2 3 4 1,2,3,4, 1,2,3,4, 1,2,3,4, 1,2,3,4, 1 2 3 4 1,2,3,4, 1,2,3,4, 1,2,3,4, 1、2、3、4 1+2+3×4 1,2,3,4 1+2+3+4+.