219. Find the derivative of the function $y=1 / x^{3}$.






The text has been translated while preserving the original line breaks and format.
Solution. Using a negative exponent, we transform the given function to $1 / x^{3}=x^{-3}$. Then we get

$$
\left(1 / x^{3}\right)^{\prime}=\left(x^{-3}\right)^{\prime}=-3 x^{-3-1}=-3 x^{-4}=-3 \cdot \frac{1}{x^{4}}=-\frac{3}{x^{4}}
$$