## Precalculus: Mathematics for Calculus, 7th Edition

$$\frac{1}{72}$$
$Evaluate$ $the$ $expression:$ $$2^{-3}-3^{-2}$$ $$2^{-3}-3^{-2} = \frac{1}{2^3}-\frac{1}{3^2}$$ $$\frac{1}{2\times2\times2}-\frac{1}{3\times3}$$ $$\frac{1}{8}-\frac{1}{9}$$ Find the least common denominator [72] $$\frac{1\times9}{8\times9}-\frac{1\times8}{9\times8}$$ $$\frac{9}{72}-\frac{8}{72} = \frac{1}{72}$$