Ответ:

а) \(\frac{x^2-y^2}{(x+y)^2}=\frac{(x-y)(x+y)}{(x+y)^2}=\frac{x-y}{x+y}\).

б) \(\frac{(x-y)^2}{x^2-y^2}=\frac{(x-y)^2}{(x-y)(x+y)}=\frac{x-y}{x+y}\).

в) \(\frac{x^2-9}{x^2+6x+9}=\frac{(x-3)(x+3)}{(x+3)^2}=\frac{x-3}{x+3}\).

г) \(\frac{x^2-10x+25}{x^2-25}=\frac{(x-5)^2}{(x-5)(x+5)}=\frac{x-5}{x+5}\).

Ответ: а) \(\frac{x-y}{x+y}\); б) \(\frac{x-y}{x+y}\); в) \(\frac{x-3}{x+3}\); г) \(\frac{x-5}{x+5}\).