(1)1999+9992,
=1999+999×999,
=1999+(1000-1)×999,
=1999+999000-999,
=(1999-999)+999000,
=1000+999000,
=1000000;
(2)+++…+,
=-+-+-+…+-,
=;
(3)2008×20092009-2009×20082008,
=2008×(2009×10001)-2009×(2008×10001)
=2008×10001×(2009-2009),
=2008×10001×0,
=0;
(4)÷6+×,
=×+×,
=(+)×,
=×,
=;
(5)5.58-+5.42-,
=(5.58+5.42)-(+),
=11-1,
=10;
(6)(2890+++)÷(++),
=[2890+(++)]÷(++),
=2890÷(++)+(++)÷(++),
=2890×+1,
=1200+1,
=1201;
(7)3333×3333+9999×8889
=9×1111×1111+9999×8889,
=9999×1111+9999×8889,
=9999×(1111+8889),
=9999×10000,
=99990000;
(8)2005+2006×2004 |
2005×2006-1 |
,
=2005+(2005+1)×2004 |
2005×(2005+1)-1 |
,
=2005+2005×2004+2004 |
2005×2005+2005-1 |
,
=2005×2005+2004 |
2005×2005+2004 |
,
=1;
(9)因为2!=2×3,3!=3×4×5,5!=5×6×7×8×9,
所以4!=4×5×6×7=840 6!=6×7×8×9×10×11,
所以==.