The laws of logarithms, in particular the power law \(\log_c \left(x^n\right)=n\log_c (x)\), can only be applied when the base of the argument is positive in value (\(x \gt 0\)).
The domain of the function \(f(x)=\log_2 \left(4x^3\right)\) is \(\{x \mid x \gt 0, x\in\mathbb{R}\}\). Applying the laws of logarithms within the domain of the function provides us with an equivalent equation for the function, \(f(x)=2+3\log_2 (x)\).
The domain of \(g(x)=\log_2 \left(x^2\right)\) is \(\{x \mid x\neq0, x\in\mathbb{R}\}\). The power law cannot be applied to this equation within the domain of \(g(x)\). Thus \(g(x)=\log_2 \left(x^2\right)\) and \(h(x)=2\log_2 (x)\) are not equivalent forms of the same function.
Note: An equivalent equation for the graph of \(g(x)\) would be \(g(x)=2\log_2 \lvert x\rvert\).