from above?一道题limX→-∞(X^2+X+3)/X^2最后答案怎么会是1from above?1我懂,from above或者from below怎么回事?怎么判断?

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from above?一道题limX→-∞(X^2+X+3)/X^2最后答案怎么会是1from above?1我懂,from above或者from below怎么回事?怎么判断?
from above?
一道题limX→-∞
(X^2+X+3)/X^2
最后答案怎么会是1from above?
1我懂,from above或者from below怎么回事?怎么判断?

from above?一道题limX→-∞(X^2+X+3)/X^2最后答案怎么会是1from above?1我懂,from above或者from below怎么回事?怎么判断?
(X^2+X+3)/X^2=1+1/x+1/x^2
当X→-∞,第2项→-0,第3项→0(注意第2项的趋势!)
结果比1要小点.

是不是左极限,右极限啊