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November 01, 2025, 04:18:04 pm
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Author Topic: Second derivative question help?  (Read 1048 times)  Share 

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TMJ

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Second derivative question help?
« on: August 04, 2013, 09:46:30 pm »
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If y=e^kx and d^2y/dx^2 -3dy/dx -4y=0, find the value of k

So far I have found the derivative and second derivative of e^kx and substituted into the equation to get

k^2e^kx-3(ke^kx)-4e^kx=o

It seems I have to solve this via quadratic methods but I dont know how so can someone please help?

Thank you
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RKTR

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Re: Second derivative question help?
« Reply #1 on: August 04, 2013, 09:53:23 pm »
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k^2e^kx-3(ke^kx)-4e^kx=0

(e^kx)(k^2-3k-4)=0

(e^kx)(k-4)(k+1)=0


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lzxnl

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Re: Second derivative question help?
« Reply #2 on: August 04, 2013, 10:19:15 pm »
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lol let k = -infinity when x>0 and k = infinity when x<0 :D
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BubbleWrapMan

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Re: Second derivative question help?
« Reply #3 on: August 08, 2013, 06:16:58 pm »
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Quote from: nliu1995 on August 04, 2013, 10:19:15 pm
lol let k = -infinity when x>0 and k = infinity when x<0 :D
?
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