8а^2b^2 - 72a^2c^8
8(a^2b^2 - 9a^2c^8)
8a^2(b^2 - 9c^8)
8a^2(b - 3c^4)(b + 3c^4)

3x^2 - 48xy + 192y^2
3(x^2 - 16xy + 64y^2)
3(x - 8y)^2

-8a^3 + 8a^3 - 2a
0

5a^3 - 40b^6
5(a^3 - 8b^6)
5(a - 2b^2)(a^2 + 2ab^2 + 4b^4)

a - 3b - a^2 - 9b^2
-(a^2 - a) - 9(b^2 + 3b)
-(a(a - 1) - 9(b(b + 3)))
-(a - 3)(a + 3)(b + 1)(b - 3)

ac^4 - c^4 - ac^2 + c^2
c^2(a - 1)(a + 1)(c - 1)(c + 1)