find the intervals of increase and decrease of f(x)=3/(x*2+11) -1 ?

Question

My f'(x) is-6x/(x^2+1)^2, after that i didn't know how to proceed next bcus i didn't know how to find x to substitute in the f'(x).

Answer 1

Assuming your f' is correct, f is increasing where f'>0.

Since the denominator is always positive, f is increasing where the numerator is positive: x<0

Similarly for decreasing.