Derivative of y=x^4*ln4x

1. Apply the product rule:

   $$\frac{d}{d x} f{\left(x \right)} g{\left(x \right)} = f{\left(x \right)} \frac{d}{d x} g{\left(x \right)} + g{\left(x \right)} \frac{d}{d x} f{\left(x \right)}$$

   $f{\left(x \right)} = x^{4}$; to find $\frac{d}{d x} f{\left(x \right)}$:

   1. Apply the power rule: $x^{4}$ goes to $4 x^{3}$

   $g{\left(x \right)} = \log{\left(4 x \right)}$; to find $\frac{d}{d x} g{\left(x \right)}$:

   1. Let $u = 4 x$.

   2. The derivative of $\log{\left(u \right)}$ is $\frac{1}{u}$.

   3. Then, apply the chain rule. Multiply by $\frac{d}{d x} 4 x$:

      1. The derivative of a constant times a function is the constant times the derivative of the function.

         1. Apply the power rule: $x$ goes to $1$

         So, the result is: $4$

      The result of the chain rule is:

      $$\frac{1}{x}$$

   The result is: $4 x^{3} \log{\left(4 x \right)} + x^{3}$

2. Now simplify:

   $$x^{3} \left(4 \log{\left(4 x \right)} + 1\right)$$

The answer is:

$$x^{3} \left(4 \log{\left(4 x \right)} + 1\right)$$