Posted by HELP!! on .
Find the derivative of f. you may simplify before differentiating
f(x)= x27x+12/x48x3+13x2+30x72

Calculus 
Reiny,
Surely you meant ...
f(x) = (x^27x+12)/(x^48x^3+13x^2+30x72)
= (x3)(x4)/(x^48x^3+13x^2+30x72)
I checked by synthetic division if those factors are contained in the denominator, and they are, so
= 1/(x^2  x  6)
= (x^2  x  6)^1
f '(x) = (x^2  x  6)^2 (2x1)
= (1  2x)/(x^2  x  6)^2