1989+1988+1987-1986-1985-1984+1983+1982+1981-.+9+8+7-6-5-4+3+2+1
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/27 04:48:17
![1989+1988+1987-1986-1985-1984+1983+1982+1981-.+9+8+7-6-5-4+3+2+1](/uploads/image/z/33122-2-2.jpg?t=1989%EF%BC%8B1988%EF%BC%8B1987%EF%BC%8D1986%EF%BC%8D1985%EF%BC%8D1984%EF%BC%8B1983%EF%BC%8B1982%EF%BC%8B1981%EF%BC%8D.%2B9%EF%BC%8B8%EF%BC%8B7%EF%BC%8D6%EF%BC%8D5-4%EF%BC%8B3%EF%BC%8B2%EF%BC%8B1)
1989+1988+1987-1986-1985-1984+1983+1982+1981-.+9+8+7-6-5-4+3+2+1
1989+1988+1987-1986-1985-1984+1983+1982+1981-.+9+8+7-6-5-4+3+2+1
1989+1988+1987-1986-1985-1984+1983+1982+1981-.+9+8+7-6-5-4+3+2+1
=(1989-1986)+(1988-1985)+(1987-1984)+(1982-1979)+...+(9-6)+(8-5)+(7-4)+3+2+1
=3+3+...+3+3+2+1
每6项构成3个3相加.(1989-3)=1986项
上式=1986/6×3×3+3+2=1=2985