How do you find the derivative of #y=ln(-(4x^4)/(x^3-3))^5#?

1 Answer
Oct 22, 2017

#y'=-(5(12-x^3))/(x(x^3-3))#

Explanation:

The function in the general form:

#y=ln(f(x))#

then its derivative is

#y'=1/f(x)*f'(x)#

where #f(x)=(color(red)g(x))^5#

and its derivative is:

#f'(x)=5(color(red)g(x))^4*g'(x)#

where #color(red)(g(x)=-(4x^4)/(x^3-3))#

and its derivative is:

#g'(x)=((-4*4x^3)(x^3-3)-(-4x^4)(3x^2))/(x^3-3)^2#

#=(-16x^6+48x^3+12x^6)/(x^3-3)^2#

#=(48x^3-4x^6)/(x^3-3)^2=(4x^3(12-x^3))/(x^3-3)^2#

Finally, it is:

#y'=1/(color(red)g(x))^5*5(color(red)g(x))^4*g'(x)#

#=1/(-(4x^4)/(x^3-3))^cancel5*5cancel((-(4x^4)/(x^3-3))^4)*(4x^3(12-x^3))/(x^3-3)^2#

#=-(5cancel((x^3-3)))/(cancel4x^cancel4)*(cancel(4x^3)(12-x^3))/(x^3-3)^cancel2#

#=-(5(12-x^3))/(x(x^3-3))#