(1+1/16+1/17+1/18)×(1/16+1/17+1/18+1/19)-(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)=
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(1+1/16+1/17+1/18)×(1/16+1/17+1/18+1/19)-(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)=
(1+1/16+1/17+1/18)×(1/16+1/17+1/18+1/19)-(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)=
(1+1/16+1/17+1/18)×(1/16+1/17+1/18+1/19)-(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)=
=[(1+1/16+1/17+1/18)*(1/16+1/17+1/18)+(1+1/16+1/17+1/18)*1/19)]-[(1+1/16+1/17+1/18)*(1/16+1/17+1/18)+(1/19*(1/16+1/17+1/18))]=1/19*[(1+1/16+1/17+1/18)-(1/16+1/17+1/18)]=1/19
19分之1
(1+1/16+1/17+1/18)×(1/16+1/17+1/18+1/19)-(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)
=(1/16+1/17+1/18+1/19)+[(1/16+1/17+1/18)(1/16+1/17+1/18+1/19)-
(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)]
=...
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(1+1/16+1/17+1/18)×(1/16+1/17+1/18+1/19)-(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)
=(1/16+1/17+1/18+1/19)+[(1/16+1/17+1/18)(1/16+1/17+1/18+1/19)-
(1+1/16+1/17+1/18+1/19)×(1/16+1/17+1/18)]
=(1/16+1/17+1/18+1/19)+(1/16+1/17+1/18)[([1/16+1/17+1/18+1/19-1-1/16-1/17-1/18-1/19]
=1/16+1/17+1/18+1/19+(1/16+1/17+1/18)(-1)
=1/16+1/17+1/18+1/19-1/16-1/17-1/18
=1/19
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