原式=[(2^2-1^2)/2^2]*[(3^2-1^2)/3^2]*...*[(2011^2-1^2)/2011^2] =[(1*3)/2^2]*[(2*4)/3^2]*...*[(2010*2012)/2011^2] =(1/2)*(2012/2011) =1006/2011
