2011/2012×2011
=2011/2012×(2012-1)
=2011/2012×2012-2011/2012×1
=2011-2011/2012
=2010又1/2012
可设2011=a, 则2012=a+1
原式=a²/(a+1)
=[(a+1)²-2(a+1)+1]/(a+1)
=a+1-2+[1/(a+1)]
=a-1+[1/(a+1)]
=2010+(1/2012)
≈2010+0.000497
=2010.000497
(2011/2012) ×2011
=[1-(1/2012)] ×2011
=2011-2011/2012
=2010+1/2012
2011 /2012 =1- 1/2012
=>(2011/2012)*2011=(1- 1/2012 )*2011=2011 - 2011/2012=2010+ 1/2012
2011
------- ×2011 =(2012-1)/2012 *2011=(1-1/2012)*2011=2011-2011/2012=2010+1/2012
2012