Сократите дробь: a) $$rac{15xy^5}{40x^3y^4}$$; б) $$rac{2x^2 + 12x}{12x}$$; в) $$rac{a^2 - 36}{3a + 18}$$

a) $$rac{15xy^5}{40x^3y^4} = rac{3 cdot 5 cdot x cdot y^4 cdot y}{8 cdot 5 cdot x cdot x^2 cdot y^4} = rac{3y}{8x^2}$$

б) $$rac{2x^2 + 12x}{12x} = rac{2x(x + 6)}{12x} = rac{x + 6}{6}$$

в) $$rac{a^2 - 36}{3a + 18} = rac{(a - 6)(a + 6)}{3(a + 6)} = rac{a - 6}{3}$$