Let f be a differentiable function. Let F(x)=[ln f (3x)]^2 Then what if f'(x)?

Question

baldymcgee6 · Answer

just differentiate implicitly i would say.

turingtest · Answer

assuming that F(x) is the antiderivative of f(x), then you would want to take the derivative twice
are you sure you typed this up right?

baldymcgee6 · Answer

Then solve for f'

turingtest · Answer

but the f in the problem is f(3x), not f(x)....

turingtest · Answer

is F the antiderivative of f ???

anonymous · Answer

No idea. it gave me 4 choices

a) 1/[f(3x)]^2
B) 2 ln f(3x) x f'(3x)/(3x)
C) 1/f(3x)^2
D) 6 ln f(3x) x f'(3x)/f(3x)

turingtest · Answer

and you want f', not F', correct?

anonymous · Answer

i think so

anonymous · Answer

that's how my professor wrote it..

anonymous · Answer

i don't know how to take that derivative cause there's an f.

turingtest · Answer

you must be looking for F'(x) not f'(x) because F''(x) is not a choice

anonymous · Answer

3?

anonymous · Answer

i honestly don't know, i'm under a time limit for this homework and I also have one more question to ask

turingtest · Answer

I can't give you the answer, I can only help you towards it

turingtest · Answer

typo$$\frac d{dx}f(3x)=3f'(3x)$$