这两道题，都要简便方法，谢谢各位
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1原式=(1/7)*(8*9+5*9+5*6)/(5*6*8*9)
=147/(5*6*8*9)/7
=21/(5*6*8*9)
=7/(5*6*8*3)
=7/720
2原式=[(1/2+1/4+1/8+1/16+1/32+1/64+1/64)-1/64]÷(7/4)
=[(1/2+1/4+1/8+1/16+1/32+1/32)-1/64]÷(7/4)
=[(1/2+1/4+1/8+1/16+1/16)-1/64]÷(7/4)
=[(1/2+1/4+1/8+1/8)-1/64]÷(7/4)
=(1-1/64)÷7×4
=9/16
=147/(5*6*8*9)/7
=21/(5*6*8*9)
=7/(5*6*8*3)
=7/720
2原式=[(1/2+1/4+1/8+1/16+1/32+1/64+1/64)-1/64]÷(7/4)
=[(1/2+1/4+1/8+1/16+1/32+1/32)-1/64]÷(7/4)
=[(1/2+1/4+1/8+1/16+1/16)-1/64]÷(7/4)
=[(1/2+1/4+1/8+1/8)-1/64]÷(7/4)
=(1-1/64)÷7×4
=9/16
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