1993+1994+1995+1996+1997+1998+1999+2000=______.
1993+1994+1995+1996+1997+1998+1999+2000=______.
计算:2000×1999-1999×1998+1998×1997-1997×1996+…+2×1=______.
1997+1996-1995-1994+1993+1992…-2+1=______.
1999-1998+1997-1996+…+3-2+1=______
1+2-3-4+5+6-7-8+9+…+1994-1995-1996+1997+1998=______.
19992-2000×1998=______.
1992+1994+1996+1998+2000+2002+2004+2006+2008=______.
125×(4+8)=______×______+______×______.
填质数:21=______+______=______×______=______-______.
有一个自然数a,满足a2=1993×1994×1995×1996+1,则a=______.
计算:1994×199319931993-1993×199419941994=______.
计算:3-5+7-9+11-13+…+1995-1997+1999=______.