Сократите дробь: a) $$rac{14ab^3}{49a^2b^2}$$; б) $$rac{3x}{x^2 + 4x}$$; в) $$rac{y^2 - z^2}{2y+2z}$$

a) $$rac{14ab^3}{49a^2b^2} = \frac{2b}{7a}$$
б) $$\frac{3x}{x^2 + 4x} = \frac{3x}{x(x+4)} = \frac{3}{x+4}$$
в) $$\frac{y^2 - z^2}{2y+2z} = \frac{(y-z)(y+z)}{2(y+z)} = \frac{y-z}{2}$$