# Hello Community. I could use some help on these calculus problems (Derivitiv). Thanks

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• Oct 29th 2009, 06:14 PM
giants1080
Hello Community. I could use some help on these calculus problems (Derivitiv). Thanks
1.differentiate the function using the quotient rule.
fx=cos(5x)/x^4
2.fx=(x+3)/(x-2). Derivitive?
3.
http://www.webassign.net/cgi-bin/sym...%28x%2B7%29%29Derivitive?
4.
http://www.webassign.net/cgi-bin/sym...5%20csc%28s%29derivitive?
5.

http://www.webassign.net/cgi-bin/sym...%2A%2A2%2B2%29derivitive

6.Find the second derivative of the function.

f(x) = 2x + 25x−2

7.Find f '''(x).
http://www.webassign.net/cgi-bin/sym...0%3D%202-6%2Fx
• Oct 29th 2009, 06:18 PM
artvandalay11
it seems as though you're stuck with the quotient rule, how about you try one and I'll see where you're having problems and try to help you
• Oct 29th 2009, 06:25 PM
giants1080
ok thank you. I have tried all of them and got wrong answers. I will try number 2.
fx= (x+3)/(x+2)
=x+2-x-3/x^2+4x+4
=-1/x^2+4x+4??
• Oct 29th 2009, 06:30 PM
artvandalay11
Quote:

Originally Posted by giants1080
ok thank you. I have tried all of them and got wrong answers. I will try number 2.
fx= (x+3)/(x+2)
=x+2-x-3/x^2+4x+4
=-1/x^2+4x+4??

So i think you want the deriv of f(x)

$f(x)=\frac{x+3}{x+2}$

$f'(x)=\frac{(x+2)\cdot 1-(x+3)\cdot 1}{(x+2)^2}$

and simplify from there

Notice that the first '1' is the deriv of the numerator and the second '1' is the deriv of the denominator