已知n(n+1)(n+2)分之1=n(n+1)分之A-(n+1)(n+2)分之b

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收藏|2019/02/14 19:07

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2019/02/14 19:21

a/{n(n+1)]-b/[(n+1)(n+2)]=[a(n+2)-b*n]/[n(n+1)(n+2)]=(an+2a-bn)/[n(n+1)(n+2)]=[(a-b)n+2a]/[n(n+1)(n+2)]所以a-b=0,a=b2a=1,a=1/2a=b=1/2a+b=1/2+1/2=1

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