(1+1/2+1/3+...+1/99)×(1/2+1/3+1/4+...+1/100)—(1+1/2+1/3+1/4+...14/100)×(1/2+1/3+...+1/99)=

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(1+1/2+1/3+...+1/99)×(1/2+1/3+1/4+...+1/100)—(1+1/2+1/3+1/4+...14/100)×(1/2+1/3+...+1/99)=(1+1/2+1/3

(1+1/2+1/3+...+1/99)×(1/2+1/3+1/4+...+1/100)—(1+1/2+1/3+1/4+...14/100)×(1/2+1/3+...+1/99)=
(1+1/2+1/3+...+1/99)×(1/2+1/3+1/4+...+1/100)—(1+1/2+1/3+1/4+...14/100)×(1/2+1/3+...+1/99)=

(1+1/2+1/3+...+1/99)×(1/2+1/3+1/4+...+1/100)—(1+1/2+1/3+1/4+...14/100)×(1/2+1/3+...+1/99)=
令a=1/2+1/3+...+1/99
原式=(1+a)(a+1/100)-a(1+a+1/100)
=a(1+a)+1/100(1+a)-a(1+a)-1/100a
=1/100(1+a)-1/100a
=1/100+1/100a-1/100a
=1/100

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