Re: [微分] 漸近線的一題
※ 引述《Createeee (Ce)》之銘言:
: 試求 f﹝X﹞ = 【 X﹝X-3﹞^2】^﹝1/3﹞ 的斜漸近線
: 是有一點頭緒,但下筆後還是不會
: Ans : y = X-2
令 y = mx + b 為其漸近線, 則有 lim [ f(x) - y ] = 0
x->∞
(1)求 m
3 2 (1/3)
f(x) (x - 6x + 9x)
m = lim ----- = lim --------------- = 1
x->∞ x x->∞ x
(2)求 b
3 2 (1/3)
b = lim [ f(x) - mx ] = lim [ (x - 6x + 9x) - x ]
x->∞ x->∞
= -2
--
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◆ From: 114.46.118.81
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Let t = 1/x
3 2 (1/3)
lim [ ( x - 6x + 9x ) - x ]
x->∞
2 (1/3)
( 1 - 6t + 9t ) - 1 0
= lim --------------------------- [ --- form ]
t->0 t 0
L' 6t - 2
= lim ------------------------
t->0 [ ( 1 - 3t )^2 ]^(2/3)
= -2
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>//////< 感謝強者 suhorng 大提醒
※ 編輯: BaBi 來自: 36.234.220.124 (01/31 20:52)
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