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2÷(1×3)+2÷(3×5)+2÷(5×7)+2÷(7×9)=
人气:423 ℃ 时间:2020-05-23 06:25:49
解答
=1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13+1/13-1/15
=1-1/15
=14/15不太懂~~
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