1. Identifiziere die Quadrate:

$9a^2 = (3a)^2 \implies a = 3a$

$\frac{16}{25} = (\frac{4}{5})^2 \implies b = \frac{4}{5}$

2. Wende die 3. Binomische Formel an:

$(a - b)(a + b) = a^2 - b^2$

Daher: $9a^2 - \frac{16}{25} = (3a - \frac{4}{5})(3a + \frac{4}{5})$