1又2009分之1乘2008又2009分之一
=2010/2009x(2009-2008/2009)
=2010/2009x2009-2010/2009x2008/2009
=2010-(1+1/2009)x(1-1/2009)
=2010-1+1/2009x2009
=2009+1/4036081
=2009又1/4036081
1又2009分之1乘2008又2009分之一
=2010/2009x(2009-2008/2009)
=2010/2009x2009-2010/2009x2008/2009
=2010-(1+1/2009)x(1-1/2009)
=2010-1+1/2009x2009
=2009+1/4036081
=2009又1/4036081