数学计算题(设元法)
(1/11+1/12+1/13+1/14+1/15)*(1/12+1/13+1/14+1/15+1/16)-(1/11+1/12+1/12+1/14+1/15+1/16)*(1/12+1/13+1/14+1/15）
人气：328 ℃ 时间：2020-05-25 17:26:45
解答
设t=1/12+1/13+1/14+1/15,
则原式=(1/11+1/t)*(1/t+1/16)-(1/11+1/t+1/16)*t=t/11+t^2+1/(11*16)+t/16-t/11-t^2-t/16
=1/(11*16)
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