Integration in parts: int [ 3 ( ln(7x) )^2 ] dx

[insanerp]

Evaluate the integral.

The question is attached in one link and my answer is in another. Why is my answer worry and did I do wrong?
Thanks.

 

[galactus]

I don't know what you have done wrong, but try parts.

\(\displaystyle 3\int{ln(7x)^{2}}dx\)

Let \(\displaystyle u=ln(7x)^{2}, \;\ dv=dx, \;\ du=\frac{2ln(7x)}{x}dx, \;\ v=x\)