大一高数,求教 请问第1,2题怎么做

大一高数,求教请问第1,2题怎么做
2025-05-12 14:42:40
推荐回答(2个)
回答1:

1.
lim n[ln(n-1)-lnn]
=lim ln[(n-1)/n]ⁿ
=lim ln(1- 1/n)ⁿ
=lim ln{[1+ 1/(-n)]⁻ⁿ}⁻¹
=ln(e)⁻¹
=-1
选A
2.
lim[x²/(x+1)-ax-b]
=lim[(x²-ax²-ax-bx-b)/(x+1)]
=lim[(1-a)x²-(a+b)x -b]/(x+1)
=lim[(1-a)x -b/(x+1) -(a+b)]
极限等于0,则
1-a=0,a+b=0
解得a=1,b=-1
选C

回答2: