1-2^2+3^2-4^2+5^2-6^2+ ……+2007^2-2008^2+2009^2-2010^2
=1^2-2^2+3^2-4^2+5^2-6^2+ ……+2007^2-2008^2+2009^2-2010^2
=(1^2-2^2)+(3^2-4^2)+(5^2-6^2)+……+(2009^2-2010^2)
=(1-2)(1+2)+(3-4)(3+4)+(5-6)(5+6)+……+(2009-2010)(2009+2010)
=-3-7-11-15-……-4019
=-(3+4019)×1005/2
=-2 021 055
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