# What's Wrong With My Answer?

1. ### moe darklight

357
1. The problem statement, all variables and given/known data

y = (3x)^x

(find y' )

2. Relevant equations

y = a^x
y' = (a^x)(ln(a))

and the chain rule

3. The attempt at a solution

3((3x)^x)(ln(3x))

2. ### rock.freak667

6,231
Take ln of both sides of the equation

lny=x*ln(3x)

Now use implicit differentiation

3. ### moe darklight

357
yes, that was the answer that was provided; but I don't understand why my answer is incorrect, given the fact that the derivative of a^x is (a^x)(lin(a)) and the formula seems to be of that form.

4. ### rock.freak667

6,231
I believe for that equation to work 'a' must be a constant.

357
O, thanks.