498²-4=498²-2²
=(498+2)×(498-2)
=500×496=248000
256²-244²
=(256+244)×(256-244)
=500×12=6000
2008+2008²-2009²
=2008(2008+1)-2009²
=2008×2009-2009²
=2009×(2008-2009)
=2009×(-1)
=-2009
996²-16
=996-4²
=(996+4)×(996-4)
=1000×992
=992000
2005003-2003
=(2003000+2003)-2003
=2003000
1001²-202202+101²
=(1000+1)-202202+(100+1)²
=1000000+2000+1-202202+10000+200+1
=1010000+2000+200+2-202202
=1010000-(202202-2202)
=1010000-200000
=810000