(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)=
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/06 13:02:57
![(-1)+(+2)+(-3)+(+4)...+(-41)+(+42)=](/uploads/image/z/1711499-59-9.jpg?t=%28-1%29%2B%28%2B2%29%2B%28-3%29%2B%28%2B4%29...%2B%28-41%29%2B%28%2B42%29%3D)
(-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