小学数学简便运算题1-2/3-2/9-2/27-2/81-2/243-2/7293/4+3/28+3/70+3/130+3/208 2005+2006×2004 ———————— 2005×2006-1

【1】.1-2/3-2/9-2/27-2/81-2/243-2/729
=1/3-2/9-2/27-2/81-2/243-2/729
=1/9-2/27-2/81-2/243-2/729
=····
=1/729
【2.】3/4+3/28+3/70+3/130+3/208
=(1-1/4)+(1/4-1/7)+(1/7-1/10)+(1/101/13)+(1/13-1/16)
=1- 1/16
=15/16
【3.】 2005+2006×2004
————————
2005×2006-1
2005+(2005+1)(2005-1)
=------------------------
2005×（2005+1）-1
2005+2005*2005-1
=------------------
2005*2005+2005-1
2005*2005+2004
=---------------
2005*2005+2004
=1