第七题怎么 求解!!!
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解:
1/(n+√n)+ 1/(n+√n)+...+1/(n+√n)<1/(n+1)+ 1/(n+√2)+...+1/(n+√n)<1/(n+1)+ 1/(n+1)+...+1/(n+1)
n/(n+√n)<1/(n+1)+ 1/(n+√2)+...+1/(n+√n)<n/(n+1)
lim n/(n+√n)
n→∞
=lim 1/[1 +√(1/n)]
n→∞
=1/(1+0)
=1
lim n/(n+1)
n→∞
=lim 1/(1 + 1/n)
n→∞
=1/(1+0)
=1
由夹逼准则,得:
lim [1/(n+1)+ 1/(n+√2)+...+1/(n+√n)]=1
n→∞
1/(n+√n)+ 1/(n+√n)+...+1/(n+√n)<1/(n+1)+ 1/(n+√2)+...+1/(n+√n)<1/(n+1)+ 1/(n+1)+...+1/(n+1)
n/(n+√n)<1/(n+1)+ 1/(n+√2)+...+1/(n+√n)<n/(n+1)
lim n/(n+√n)
n→∞
=lim 1/[1 +√(1/n)]
n→∞
=1/(1+0)
=1
lim n/(n+1)
n→∞
=lim 1/(1 + 1/n)
n→∞
=1/(1+0)
=1
由夹逼准则,得:
lim [1/(n+1)+ 1/(n+√2)+...+1/(n+√n)]=1
n→∞
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