小学数奥题:(1+2/5) ×(1-2/5) ×(1+2/7) ×(1-2/7) ×…………×(1+2/2005) ×(1-2/2005)

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小学数奥题:(1+2/5) ×(1-2/5) ×(1+2/7) ×(1-2/7) ×…………×(1+2/2005) ×(1-2/2005)
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小学数奥题:(1+2/5) ×(1-2/5) ×(1+2/7) ×(1-2/7) ×…………×(1+2/2005) ×(1-2/2005)
小学数奥题:(1+2/5) ×(1-2/5) ×(1+2/7) ×(1-2/7) ×…………×(1+2/2005) ×(1-2/2005)

小学数奥题:(1+2/5) ×(1-2/5) ×(1+2/7) ×(1-2/7) ×…………×(1+2/2005) ×(1-2/2005)
(2007/5) ×(3/2005)
(7/5)x(3/5)x(9/7)x(5/7)x...x(2007/5)x(2003/2005)
=[(7/5)x(9/7)x.X(2007/5)]x[(3/5)x(5/7)x...x(2003/2005)]
=(2007/5)x(3/2005)
=6021/10025

(1+2/5)×(1-2/5)×(1+2/7)×(1-2/7)×.......×(1+2/2005)×(1-2/2005)
=7/5×3/5×9/7×5/7×...×2007/2005×2003/2005
=(7/5×9/7×...×2007/2005)×(3/5×5/7×...×2003/2005)
=2007/5×3/2005
=6021/10025