爱随心飞
幼苗
共回答了23个问题采纳率:73.9% 举报
[(2n-1)^2+1]/[(2n-1)^2-1]
=(4n^2-4n+2)/(4n^2-4n)
=(4n^2-4n)/(4n^2-4n)+2/(4n^2-4n)
=1+1/[2n(n-1)]
=1+1/2*[1/(n-1)-1/n]
此处7=2*4-1
99=2*50-1
所以n从4到50,由47个
所以原式=1+1/2*(1/3-1/4)+……+1+1/2*(1/49-1/50)
=47+1/2*(1/3-1/50)
=47+47/300
1年前
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