1+2+3+4+······+78+79+801/2+1/6+1/12+1/20+······+1/72+1/90100-99+9_数学解答

1+2+3+4+······+78+79+80
1/2+1/6+1/12+1/20+······+1/72+1/90
100-99+98-97+96-······+4-3+2-1
1000-1-2-3-4-······-78-79-80
1/15+2/15+······+13/15+14/15
注：例 1/15 就是十五分之一

人气：326 ℃　时间：2020-03-24 11:59:40

解答

1+2+3+4+······+78+79+80=（1+80）*（80/2）=81*40=32401/2+1/6+1/12+1/20+······+1/72+1/90=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+.-1/90=1-1/90=89/90100-99+98-97+96-······+4-3+2-1=1*50=501000-1-2...