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Calc helpp please

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SierraMist
Posts: 116 - Karma: 13
Does anyone know how to figure out the second derivative of:

f(x) = (x3 – 5)4
Jan 29 2010 1:31PM
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DutchhGutss
Posts: 896 - Karma: 124
Is there another equation that goes with it? I remember doing these last year and usually you replace f of x into another equation then solve.
Jan 29 2010 1:39PM
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sstricky
Posts: 1876 - Karma: 111
assuming that its   f(x) = (x^3 - 5) ^4

the ^ means to the power...

so you have to use power rule.. so 1st deriv will equal

y'  =  4* 2x^2 (x^3 - 5)^3

then to do second u have to do product rule and power rule.

someone else do it.. im too lazy, if its not done in 10 minutes ill do it
Jan 29 2010 1:45PM
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Skiingslikewhoa
Posts: 426 - Karma: 12
Is it supposed to be (x^3-5)^4?

If so I got

12x^2(x^3-5)^3

for the first derivative

then

24x(x^3-5)^3+108x^4(x^3-5)^2

for the second derivative

which can be reduced to

4x(x^3-5)^2[6x(x^3-5)+27x^3]
Jan 29 2010 1:46PM
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benk
Posts: 1342 - Karma: 988
I'm most likely wrong but could you use the product rule f(x)=3x-5 g(x)=4?

I just went over the product rule last class so I dont know a lot about it
Jan 29 2010 1:55PM
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dwgreene14
Posts: 69 - Karma: 10
not if its raised to the 4th. i mean you could but not worth it when you could just use a chain rule
Jan 29 2010 2:40PM
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Dirty.Harry.
Posts: 1779 - Karma: 351
Use chain rule the first time. Then product rule and chain rule. It's a bit mean...

There's your answer:
108 x^4 (-5 + x^3)^2 + 24 x (-5 + x^3)^3
Jan 29 2010 3:08PM
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