只要變量和為1,那么可知函數(shù)值和為2,因為所求的首項和末項的變量和為1,那么可知函數(shù)值和為2,第二項與倒數(shù)第二項和為2,依次類推中間項為f(
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)=1,得到表達式的和為7.
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