(1+3+5+…+1991)-(2+4+6+…+1990)=
(1+3+5+7+……+1991)-(2+4+6+8+…+1990)=?
(1+3+5+…+1991)-(2+4+6+…+1990)=
简算:(1+3+5+7+…+1991)-(2+4+6+8+…+1990)
(2+4+6+…+1992+1994)—(1+3+5+…+1991+1993)=?
1+2+3-4+5-6+……1989-1990+1991
1-2+3-4+5-6……+1989-1990+1991怎样简便算?
1-2+3-4+5-6……+1989-1990+1991
(1+3+7+…+1991)-(2+4+6+8+…+1990)=
简算:1-2+3-4+5-6…+1989-1990+1991
(1996+1994+1992+……+6+4+2)-(1+3+5+……+1991+1993+1995)等于多少?
1-2+3-4+5-6+……+1989-1990+1991
1减2加3减4加5减6……减1990加1991等于?