1x2+2x3+3x4+4x5+5x6+6x7+..........+2001x2002+2002x2003+2003x2004+2004x2005
=2x(1x1+1x3+2x3+2x5+3x5+3x7+..........+1001x2001+1001x2003+1002x2003+1002x2005)
=2x[1x(1+3)+2x(3+5)+3x(5+7)+..........1001x(2001+2003)+1002x(2003+2005)]
=2x(1x4+2x8+3x12+........+1001x4004+1002x2008)
=2x4x(1x1+2x2+3x3+...........+1001x1001+1002x1002) (参考公式)
=8x1002(1002+1)(2x1002+1)/6
=2686716040
不容易啊,算了大半天,希望帮得到你
参考公式 :1^2+2^2+3^2+...+n^2=n(n+1)(2n+1)/6
我来帮你解答 1/3×2004×2005×2006=2686716040
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