Re: lim∞/0=? 的判斷
※ 引述《bil193 (丁丁)》之銘言:
: 標題: lim∞/0=? 的判斷
: 時間: Sat Apr 4 14:21:23 2009
:
: 給定:
: lim p(x)=∞ lim f(x)=0
: x->a x->a
:
:
: 求lim p(x)/f(x)=?
: x->a
:
:
: 詳解寫:(以下的lim都是x->a,省略了)
:
: If lim p(x)=∞ and f(x)→0 through positive values, then lim p(x)/f(x)=∞.
:
: If f(x)→0 through negative values, then lim p(x)/f(x)=-∞.
:
: if f(x)→0 through both positive and negative values, then the limit
:
: might not exist.
:
: ====================================================
: 請問各位先進,f(x)→0 through positive values是什麼意思啊?
:
: 我猜想是"由正值逼近0";所以另一個是"由負值逼近0"。
:
: 但最後它寫"由正負值逼近0,極限值便不存在" 是啥鬼??@@
:
:
: 有沒有好心人願意幫忙一下 這個看原文詳解卻看不懂的窘境....
:
: --
: ※ 發信站: 批踢踢實業坊(ptt.cc)
: ◆ From: 124.6.13.94
: 推 keith291:從正逼近不等於從負逼近(左極限不等於右 218.166.62.175 04/04 14:50
: → keith291:極限 故極限不存在 218.166.62.175 04/04 14:51
謝謝k大解說
不過小弟另有一問題
lim f(x)=0 表示 lim f(x)=0 且 lim f(x)=0
x->a x->a+ x->a-
詳解說如果f(x)逼近0,是從0.1 0.01 0.001 0.0001(正值)去逼近0的,
就是lim ∞/0+ =∞
如果是從-0.1 -0.01 -0.001 (負值)去逼近0的,就是lim ∞/0-=-∞
應該就只有這兩種狀況而已,怎麼還會有第三種情況呢??
ps.這題是stewart微積分的習題
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 124.6.13.94
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