Form 4 M2 Limits

👨🏻‍🏫 學術台數學

Ian Langley

2011-07-20 4:38 am

http://imageshack.us/photo/my-images/837/0001le.jpg/

http://imageshack.us/photo/my-images/838/0001ep.jpg/

可唔可以教我計一計？上面那題答案係 -9 但我計黎計去都係9

下面那題我rationalize 之後，個分母最終都係 0 。可唔可幫下我。

更新1:

仲有上面那題中個infinity 係正係負其實都係咪一樣咁計？

回答 (1)

myisland8132

2011-07-20 5:02 am

✔ 最佳答案

5 lim(x-> -infinity) (9x - 4)/√(x^2 + 5x + 3)

= lim(x-> -infinity) (9 - 4/x)/√(1 + 5/x + 3/x^2)

= 9/(-1)

= -9

17 lim(x-> infinity) √(4x^2 - x) + 2x

= lim(x-> infinity) -x /[√(4x^2 - x) - 2x]

= lim(x-> infinity) -1 /[√(4 - 1/x) - 2]

= 1/4

👍 0 👎 0

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