Solution:
\( \frac{dy}{dx} = \lim \limits _{h \rightarrow 0} \frac{2(x+h)^3-2x^3}{h}=\lim \limits _{h \rightarrow 0} \frac{2x^3+6x^2h+6xh^2+2h^3-2x^3}{h}=\lim \limits _{h \rightarrow 0} \frac{6x^2h+6xh^2+2h^3}{h}=\lim \limits _{h \rightarrow 0} 6x^2+6xh+2h^2=6x^2 \)