1-2+3-4+5-6.+1991-1992+1993=?
1-2+3-4+5-6.+1991-1992+1993=?
小学四年级奥数题1-2+3-4+5-6.+1991-1992+1993
1-2+3-4+5-6...+1991-1992+1993用简便计算怎么算
计算 1-2+3-4+5-6+...+1991-1992+1993
1994-1993+1992+1991-1990+1989+1988-1987+.+5-4+3+2-1=
1-2+3-4+5-6+…+1991-1992+1993=______.
(2+4+6+…+1992+1994)—(1+3+5+…+1991+1993)=?
1994-1993+1992+1991-1990.+5-4+3+2-1=
1992/1993+1991/1993+1990/199+…+3/1993+2/1993+1/1993=?
计算:1993+1992-1991-1990+1989+1988-1987-1986+…+5+4-3-2+1=_____
1+2+3+4-5-6-7-8+...-1989-1990-1991-1992+1993+1994+1995+1996=
1-2+3-4+5-6+……+1991-1992+1993 简便算法