Выполните действия: (4a^2-1)/(4a-12):(6a+3)/(a-3).

\[\frac{4a^{2} - 1}{4a - 12}\ :\frac{6a + 3}{a - 3} =\]

\[= \frac{\left( 4a^{2} - 1 \right)(a - 3)}{4(a - 3)(6a + 3)} =\]

\[= \frac{(2a - 1)(2a + 1)}{4 \cdot 3(2a + 1)} = \frac{2a - 1}{12}.\]