平方差
=(2+1)(2-1)+(4+3)(4-3)+……+(2004+2003)(2004-2003)
=(2+1)×1+(4+3)×1+……+(2004+2003)×1
=1+2+3+4+……+2003+2004
=(1+2004)×1002
=2009010
平方差
=(2+1)(2-1)+(4+3)(4-3)+……+(2004+2003)(2004-2003)
=(2+1)×1+(4+3)×1+……+(2004+2003)×1
=1+2+3+4+……+2003+2004
=(1+2004)×1002
=2009010