6. Разложите на множители: a) \frac{1}{81}a²-0,09c4; 6) (b+8)²-4b²; в) а³-b³.

а) $$\frac{1}{81}a^2 - 0.09c^4 = (\frac{1}{9}a)^2 - (0.3c^2)^2 = (\frac{1}{9}a - 0.3c^2)(\frac{1}{9}a + 0.3c^2)$$ б) $$(b+8)^2 - 4b^2 = (b+8)^2 - (2b)^2 = (b+8-2b)(b+8+2b) = (8-b)(3b+8)$$ в) $$a^9 - b^3 = (a^3)^3 - b^3 = (a^3 - b)(a^6 + a^3b + b^2)$$