Quiz 3.2:


Question:

Use the definition of the derivative function to find \( \frac{dy}{dx} \) for \( y=2x^3 \)


Solution:

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