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1/1×3+1/3×5+1/5×7······﹢1/47×49
人气:137 ℃ 时间:2020-08-23 17:56:14
解答
1/1×3+1/3×5+1/5×7······﹢1/47×49
=1/2×(1-1/3)+1/2×(1/3-1/5)+...+1/2×(1/47-1/49)
=1/2×(1-1/'3+1/3-1/5+1/5-1/7+...+1/47-1/49)
=1/2×(1-1/49)
=24/49
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