Chapter 15 - Differentiation in Several Variables - 15.2 Limits and Continuity in Several Variables - Exercises - Page 772: 28

$$11$$

Given $$\lim _{(z, w) \rightarrow(-1,2)}\left(z^{2} w-9 z\right) $$ Since $ \left(z^{2} w-9 z\right) $ is continuous everywhere, then by substitution, we get \begin{align*} \lim _{(z, w) \rightarrow(-1,2)}\left(z^{2} w-9 z\right)&=\lim _{(z, w) \rightarrow(-1,2)}\left( 2+9\right)\\ &=11 \end{align*}