2006x2006÷2007又1/2005
=2006*2006*1/(2007*2005+1)
=2006*2006*1/(2006-1)(2006+1)+1
=2006^2/(2006^2+1-1)
=2006^2/2006^2
=1
2011÷2009又2009/2010
=2011*2010/(2009*2010+2009)
=2011*2010/2009(2010+1)
=2010/2009
=1又1/2009
2006x2006÷2007又1/2005
=2006*2006*1/(2007*2005+1)
=2006*2006*1/(2006-1)(2006+1)+1
=2006^2/(2006^2+1-1)
=2006^2/2006^2
=1
2011÷2009又2009/2010
=2011*2010/(2009*2010+2009)
=2011*2010/2009(2010+1)
=2010/2009
=1又1/2009