1+2+3+…+9+10+9+…+3+2+1等于多少 怎么算.?
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/28 11:01:27
![1+2+3+…+9+10+9+…+3+2+1等于多少 怎么算.?](/uploads/image/z/133122-66-2.jpg?t=1%2B2%2B3%2B%E2%80%A6%2B9%2B10%2B9%2B%E2%80%A6%2B3%2B2%2B1%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91+%E6%80%8E%E4%B9%88%E7%AE%97.%3F)
1+2+3+…+9+10+9+…+3+2+1等于多少 怎么算.?
1+2+3+…+9+10+9+…+3+2+1等于多少 怎么算.?
1+2+3+…+9+10+9+…+3+2+1等于多少 怎么算.?
1+2+3+…+9+10+9+…+3+2+1
=1+2+3+…+9+9+…+3+2+1+10
=2*(1+9)*9/2+10
=2*45+10
=90+10
=100
原式 =(1+2...+10)+(1+2...+9)
=(1+10)*10/2 + (1+9)*9/2
=55+45
=100