- 计算:(1)1+2-3-m+5+n-7-x+9+…+1990-1991-1992+1993+199m-1995-199n+1997+1997=______.(2)3+n+9+12+15+…+1995+199x=____...
- 简算.①125×32×25②5×15×25×125×64 ③1992+1994+1996+1998+2000+2002+2004+2006+2008.
- 已知1+2+3+4+…+98+99=4950,如果把98前面的加号改为减号,其他的数字和符号都不变,答案应是______.
- 计算89-88+87-86+…+5-4+3-2+1的结果是______.
- 已知Sn=1-2+3-4+5-6+…+(-1)n+n,其中n是正整数.那么S2001+S2002=______.
- 2+4+6+8+10+12+14+16+18=______×______.
- 计算:2010-2009-2008+2007+2006-2005-2004+2003+…+6-5-4+3+2-1.
- 100-98+96-94+…+8-6+4-2.
- 8+88+888+8888+88888=______.
- 199+299+399+499+…+9899.
- 19+28+37+46+55+64+73+82+91+______=550.
- 脱式计算(1)(612-314)÷(13+1115)(2)16+112+130+142+156(3)2.25×35+2.75÷123+60%(4)(1+3+5+…+1001)-(2+4+6+…+1...
- 1997+1996-1995-1994+1993+1992…-2+1=______.
- 2001-1998+1995-1992+…+15-12+9-6+3.
- 计算:1-3+5-7+9-11+…-1999+2001=______.