\[2a(5a + 10) + (2a - 8)(3a + 2) =\]
\[= 10a^{2} + 20a + 6a^{2} + 4a - 24a - 16 =\]
\[= 16a^{2} - 16 = 16 \cdot \left( a^{2} - 1 \right) =\]
\[= 16 \cdot (a - 1)(a + 1).\]