第十题,

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第十题,
第十题,
 

第十题,
①n/(n^2+n)+n/(n^2+n-1)+……+n/(n^2+1) < n/(n^2)+n/(n^2)+……+n/(n^2)=n^2/n^2=1

②n/(n^2+n^2)+n/(n^2+(n-1)^2)+……+n/(n^2+1^2) < n/(n^2+n)+n/(n^2+n-1)+……+n/(n^2+1)

lim(n/(n^2+n^2)+n/(n^2+(n-1)^2)+……+n/(n^2+1^2))
=lim1/n*(1/(+(n/n)^2)+ 1/(n^2+((n-1)/n)^2)+……+ 1/(n^2+(1/n)^2))
=∫1/(1+x^2)dx=arctan x|=1
根据夹逼定理,所以原极限=1

正确答案就是A~嘻嘻