1/1987*1988+1/1988*1989+1/1989*1990+……+1/1996*1997+1/1997*19
1/1987*1988+1/1988*1989+1/1989*1990+……+1/1996*1997+1/1997*19
1/1987*1988+1/1988*1989+1/1989*1990+.+1/1997*1998+1/1998*199
(1990乘1990+1988乘1988+…+2乘2)-(1989乘1989+1987乘1987+…+1)
1988+1989*1987/1988*1989-1=?
1/1986*1987+1/1987*1988+1/1988*1989+1/1989*1990+1/1990=?
1988+1989×1987÷1988×1989-1=1989-1+1989×1987÷1988×1989-1
怎样计算1/1987*1988+1/1988*1989+1/1989*1990+1/1990
1990^2-1989^2+1988^2-1987^2+……+2^2-1
99999²+199999 1986+1988+1990+…+2000分之1985+1987+1989+…+1
1\1986*1987+1\1987*1988+1\1988*1989+1\1989*1990+1\1990这个计算怎么
1990^2-1989^2+1988^2-1987^2+…+2^2-1
1988乘1989-1分之1988+1989乘1987