## Calculus with Applications (10th Edition)

$y=f[g(x)],$ $f(x)=\sqrt{x},\qquad g(x)=9-4x$
A reliable method is asking: "How would we calculate this on a calculator?". First, calculate $g(x)=9-4x$ and then, calculate: $\quad \sqrt{\text{the result, g(x)}}$ (apply $f(x)=\sqrt{x}$ on g(x) instead of x) $f[g(x)]=\sqrt{g(x)}=\sqrt{9-4x}=y$