## Calculus (3rd Edition)

According to the chain rule, $\frac{df}{dx}=\frac{df}{du}\times\frac{du}{dx}=2u\times u'$ Given that $u(2)=-5$ and $u'(2)=-5$. Therefore, $\frac{df}{dx}|_{x=2}= 2(-5)\times-5= 50$