20102009²/(20102008²+20102010²-2)
设a=20102009
故:a-1=20102008,a+1=20102010
故:20102009²/(20102008²+20102010²-2)
=a²/[(a-1)²+(a+1)²-2]
= a²/(2 a²)
=1/2
20102009²/(20102008²+20102010²-2)
设a=20102009
故:a-1=20102008,a+1=20102010
故:20102009²/(20102008²+20102010²-2)
=a²/[(a-1)²+(a+1)²-2]
= a²/(2 a²)
=1/2