1*2*3···2008*2009*(-1)*(-1/2)*(-1/3)···(-1/2008)*(1/2009)

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1*2*3···2008*2009*(-1)*(-1/2)*(-1/3)···(-1/2008)*(1/2009)

1*2*3···2008*2009*(-1)*(-1/2)*(-1/3)···(-1/2008)*(1/2009)
1*2*3···2008*2009*(-1)*(-1/2)*(-1/3)···(-1/2008)*(1/2009)

1*2*3···2008*2009*(-1)*(-1/2)*(-1/3)···(-1/2008)*(1/2009)
1*2*3···2008*2009*(-1)*(-1/2)*(-1/3)···(-1/2008)*(-1/2009) 最有有负号吧
=(-1×1)×(-1/2×2)×……×(-1/2009×2009) 共2009个数
= -1×(-1)×……×(-1) 2009个-1相乘
= -1