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(90+1/88)×1/89
=90×1/89+1/88×1/89
=89×1/89+1/89+1/88×
1/89
=1+1/89×(1+1/88)
=1+1/89×89/88
=1+1/88=89/88
=90×1/89+1/88×1/89
=89×1/89+1/89+1/88×
1/89
=1+1/89×(1+1/88)
=1+1/89×89/88
=1+1/88=89/88
追问
很难懂。
追答
怎么会呢?我省略了一步,现在加上。就是运用两次乘法分配律。
(90+1/88)×1/89
=90×1/89+1/88×1/89
=(89+1)×1/89+1/88×1/89
=89×1/89+1/89×1+1/88×
1/89
=1+1/89×(1+1/88)
=1+1/89×89/88
=1+1/88=89/88
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