Question

sorry to ask a second question so soon, but i'm just not getting this one.

if f(x)= 3x lnx, then f'(x)=?

i used
f'(x)=3x(D lnx) + D (3x) (lnx)
f'(x)=3x (1/x) + 3 (lnx)
so... f'(x)=3+3lnx or 3(1+lnx).
unfortunately that isn't one of the possible answers given. could one of you kind folks help me understand where i went wrong?

thank you

Answer 1

I am getting the same answer.

What are the other choices?

Answer 2

Wow! that was sooo fast. thank you for the help.
sorry, i should have thought to provide the answers
here they are.

a) 3+ln(x^3)
b) 1+ln(x^3)
c) (3/x)+3lnx
d) 3/(x^2)
e) 1/x

Answer 3

It is a. They used the law of logs or lns to rewrite 3 ln x as ln x^3.

Answer 4

Thank you very much. haven't touched this kind of stuff in a while. your help is much appreciated.

Answer 5

You are welcome. So many times, students know the Calculus, but it is something from past math courses that cause the issue with finding the final answer.

Answer 6

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