lim[(4+7+...+3n+1)/(n^2-n)]=

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lim[(4+7+...+3n+1)/(n^2-n)]=lim[(4+7+...+3n+1)/(n^2-n)]=lim[(4+7+...+3n+1)/(n^2-n)]=4+7+...+3n+1=(4+

lim[(4+7+...+3n+1)/(n^2-n)]=
lim[(4+7+...+3n+1)/(n^2-n)]=

lim[(4+7+...+3n+1)/(n^2-n)]=
4+7+...+3n+1=(4+3n+1)*n/2=(3n²+5n)/2
[(4+7+...+3n+1)/(n^2-n)]=(3n²+5n)/(2n²-2n)=(3+5/n)/(2-2/n)
所以 im[(4+7+...+3n+1)/(n^2-n)]=3/2

4+7+...+3n+1=(4+3n+1)n/2=n(3n+5)/2
极限化简等于lim(3n+5)/(2n-2)=3/2