## Calculus (3rd Edition)

$$y''= \frac{14}{25}x^{-12/5}.$$
Recall that $(x^n)'=nx^{n-1}$ Given $y=x^{-2/5}$, then by using the power rule, we have $$y'=-\frac{2}{5}x^{-7/5},$$ and the second derivative $y''$ is given by $$y''=-\frac{2}{5}(-\frac{7}{5})x^{-12/5}=\frac{14}{25}x^{-12/5}.$$