а) \( \frac{x^2 - 9b^2}{x+3b} = \frac{(x-3b)(x+3b)}{x+3b} = x-3b \)
б) \( \frac{6y-1}{36y^2 - 1} = \frac{6y-1}{(6y-1)(6y+1)} = \frac{1}{6y+1} \)
в) \( \frac{4a^2 - 2ab}{4a^2 - b^2} = \frac{2a(2a-b)}{(2a-b)(2a+b)} = \frac{2a}{2a+b} \)
г) \( \frac{25x^2 - y^2}{10x^2y + 2xy^2} = \frac{(5x-y)(5x+y)}{2xy(5x+y)} = \frac{5x-y}{2xy} \)
Ответ: а) \( x-3b \); б) \( \frac{1}{6y+1} \); в) \( \frac{2a}{2a+b} \); г) \( \frac{5x-y}{2xy} \).