Expanding the expression:
(2a + c)(a - 3c) + a(2c + a)
= 2a^2 - 6ac + ac - 3c^2 + 2ac + a^2= 2a^2 + ac - 6ac - 3c^2 + 2ac + a^2= 3a^2 - 4ac - 3c^2
Expanding the expression:
(2a + c)(a - 3c) + a(2c + a)
= 2a^2 - 6ac + ac - 3c^2 + 2ac + a^2
= 2a^2 + ac - 6ac - 3c^2 + 2ac + a^2
= 3a^2 - 4ac - 3c^2