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Derivatives

by courtrigrad
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courtrigrad
#1
Oct5-05, 07:23 PM
P: 1,237
Suppose [tex] f(x) = \frac{(x-3)^{4}}{x^{2}+2x} [/tex]. Find the derivative an determine the values for which it is equal to 0. So [tex] f'(x) = \frac{x^{2}+2x(4(x-3)^{3}) - (x-3)^{4}(2x+2)}{(x^{2}+2x)^{2}} [/tex]. But now how would I go about finding the values for which the derivative equals 0? [tex] f'(x) = \frac{x^{2}+2x(4(x-3)^{3}) (x-3)^{4}(2x+2)}{(x^{2}+2x)^{2}} = 0 [/tex]. Is it possible to factor?

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Jameson
#2
Oct5-05, 07:53 PM
P: 788
For any fraction, let's call it [itex]\frac{A}{B}[/itex], which part will make the whole thing equal to 0? A or B?
courtrigrad
#3
Oct5-05, 08:08 PM
P: 1,237
A

will yeah

BobG
#4
Oct5-05, 09:08 PM
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Derivatives

Quote Quote by plugpoint
Suppose [tex] f(x) = \frac{(x-3)^{4}}{x^{2}+2x} [/tex]. Find the derivative an determine the values for which it is equal to 0. So [tex] f'(x) = \frac{(x^{2}+2x)(4(x-3)^{3}) - (x-3)^{4}(2x+2)}{(x^{2}+2x)^{2}} [/tex]. But now how would I go about finding the values for which the derivative equals 0? [tex] f'(x) = \frac{x^{2}+2x(4(x-3)^{3}) (x-3)^{4}(2x+2)}{(x^{2}+2x)^{2}} = 0 [/tex]. Is it possible to factor?

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You missed a set of parentheses.
TD
#5
Oct6-05, 03:32 AM
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P: 1,021
Your derivative isn't correct yet, make sure you check that first!
HallsofIvy
#6
Oct6-05, 08:16 AM
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PF Gold
P: 39,363
The derivative is correct, assuming that the missing parentheses BobG mentions is put in correctly!


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