# how to evaluate the derivitive of the following?

• August 9th 2011, 04:29 AM
university
how to evaluate the derivitive of the following?
1)f(x)=x^2+5x-2/x+4
2)f(x)=[x^5-1/x^4]^6
• August 9th 2011, 04:39 AM
e^(i*pi)
Re: how to evaluate the derivitive of the following?
Is number 1 $f(x) = \dfrac{x^2+5x-2}{x+4}$ or $f(x) = x^2 + 5x - \dfrac{2}{x} + 4$ or even $f(x) = x^2 + 5x + \dfrac{2}{x+4}$

Same goes for number 2, please use brackets to clearly separate what is in the numerator and what is in the denominator
• August 9th 2011, 05:19 AM
Siron
Re: how to evaluate the derivitive of the following?
Is the second one:
$f(x)=\left(\frac{x^5-1}{x^4}\right)^6$
?
• August 9th 2011, 05:22 AM
university
Re: how to evaluate the derivitive of the following?
its the first one you wrote...1)f(x)=(x^2+5x-2)/(x+4)
2)f(x)=[x^5-1/(x^4)]^6
• August 9th 2011, 05:24 AM
university
Re: how to evaluate the derivitive of the following?
no its f(x) = [x^5 - 1 over x^4]^6....sry its hard to write!
• August 9th 2011, 05:25 AM
Siron
Re: how to evaluate the derivitive of the following?
For the first one: use the quotienrule.
For the second one, use:
$D[u^6]=6\cdot u^5\cdot D(u)$
• August 9th 2011, 05:45 AM
Bacterius
Re: how to evaluate the derivitive of the following?
For clarity - the OP meant those:

$f(x)=\frac{x^2+5x-2}{x+4}$

$f(x) = \left $\frac{x^5 - 1}{x^4} \right$ ^6$ (I think.. it's still ambiguous but I think he's meant to use the quotient rule in these problems)

University please consult the stickies in here, it will make it easier to communicate mathematics over the forum.
• August 9th 2011, 07:09 AM
skeeter
Re: how to evaluate the derivitive of the following?
Quote:

Originally Posted by university
no its f(x) = [x^5 - 1 over x^4]^6....sry its hard to write!

even if you do not know Latex, you can use grouping symbols where necessary ...

f(x) = [(x^5 - 1)/x^4]^6
• August 15th 2011, 09:06 AM
university
Re: how to evaluate the derivitive of the following?
so is the answer to the 1st q -4/5 and the 2nd positive infinity
• August 15th 2011, 09:19 AM
HallsofIvy
Re: how to evaluate the derivitive of the following?
??? Your original question was to find the derivatives of two functions. The answer will be two functions, not two numbers. Are you asking about evaluating the derivatives at specific values of x? If so, we would have to know the values of x!