香港寵物小精靈村落 論壇

標題: Differentiation [打印本頁]

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作者: 火火火火火    時間: 23/8/2005 08:29 AM
標題: Differentiation
It given that y=px^5 and dx/dy=3/2 at (1,Q).
Find p and q.

我有ｄ問題想問下．
第一，ｄｘ卅ｄｙ係咪ｓｌｏｐｅ？？
第二，ｙ＝５ｐｘ＾４係咪第二條ｅｑｎ？
第三，如二是，（１，ｑ）係咪個兩條ｅｑｎ一齊的交點？

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作者: 碧咸    時間: 23/8/2005 11:33 AM

Originally posted by 火火火火火 at 2005-8-23 08:29 AM:
It given that y=px^5 and dx/dy=3/2 at (1,Q).
Find p and q.

我有ｄ問題想問下．
第一，ｄｘ卅ｄｙ係咪ｓｌｏｐｅ？？
第二，ｙ＝５ｐｘ＾４係咪第二條ｅｑｎ？
第三，如二是，（１，ｑ）係咪個兩 ...

1.dy/dx先係slope
2.y唔係=px^5咩？

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作者: 細薯    時間: 23/8/2005 07:31 PM
ｅｑｎ係....equation??
===========================

第一，ｄｘ卅ｄｙ係咪ｓｌｏｐｅ？？
>>不是
dy/dx 先係
(樓上答左你)
第二，ｙ＝５ｐｘ＾４係咪第二條ｅｑｎ？
>>５ｐｘ＾４只係那條equation ( y=px^5 ) 在某x值那時的slope (ie 那條curve 在 x 值的 tangent ge slope)

y=px^5
∴ dy/dx = 5p x^4

dy/dx |(1,Q) = 5p (1)^4
dy/dx = 5p
dx/dy =3/2
∴5p= 1 / (3/2)
p= 10/3
∴y=px^5
y=10/3
Q=10/3

唔知有冇計錯...

[ Last edited by smallpotato226 on 2005-8-23 at 07:53 PM ]

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作者: 火火火火火    時間: 23/8/2005 07:56 PM
唔該....
明白哂!!

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作者: oscar    時間: 23/8/2005 11:08 PM

Originally posted by smallpotato226 at 2005-8-23 19:31:
y=px^5
∴ dy/dx = 5p x^4

dy/dx |(1,Q) = 5p (1)^4
dy/dx = 5p
dx/dy =3/2
∴5p= 1 / (3/2)
p= 10/3
∴y=px^5
y=10/3
Q=10/3

Oh no!....
這裡計錯了...
p=2/15
Q=2/15
=.="

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作者: 火火火火火    時間: 24/8/2005 08:02 AM
但是答案係q=p=3/10
...................

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作者: oscar    時間: 24/8/2005 12:06 PM

Originally posted by 火火火火火 at 2005-8-24 08:02:
但是答案係q=p=3/10
...................

但係以smallpotato既計法，應該係2/15...

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作者: 細薯    時間: 24/8/2005 09:03 PM

Originally posted by oscar at 2005-8-23 11:08 PM:

Oh no!....
這裡計錯了...
p=2/15
Q=2/15
=.="

係wor.....
D 斜搞亂了我.........orz

Originally posted by 火火火火火 at 2005-8-24 08:02 AM:
但是答案係q=p=3/10
...................

有冇抄錯左?
唔係 dx/dy=3/2 係dy/dx =3/2  ??

Originally posted by oscar at 2005-8-24 12:06 PM:

但係以smallpotato既計法，應該係2/15...

考試應該不會犯這錯.......汗"

[ Last edited by smallpotato226 on 2005-8-24 at 09:04 PM ]

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