5. Сократите дроби: \(\frac{25-y^2}{25+5y}\), \(\frac{x^2-16}{(x-4)^2}\), \(\frac{25-y^2}{(5+y)^2}\), \(\frac{(x-4)^2}{16-x^2}\), \(\frac{(m-7)^2}{14-2m}\).

1. \(\frac{25-y^2}{25+5y}=\frac{(5-y)(5+y)}{5(5+y)}=\frac{5-y}{5}\), при \(y\ne-5\).
2. \(\frac{x^2-16}{(x-4)^2}=\frac{(x-4)(x+4)}{(x-4)^2}=\frac{x+4}{x-4}\), при \(x\ne4\).
3. \(\frac{25-y^2}{(5+y)^2}=\frac{(5-y)(5+y)}{(5+y)^2}=\frac{5-y}{5+y}\), при \(y\ne-5\).
4. \(\frac{(x-4)^2}{16-x^2}=\frac{(x-4)^2}{(4-x)(4+x)}=-\frac{x-4}{x+4}=\frac{4-x}{x+4}\), при \(x\ne4,-4\).
5. \(\frac{(m-7)^2}{14-2m}=\frac{(m-7)^2}{-2(m-7)}=-\frac{m-7}{2}=\frac{7-m}{2}\), при \(m\ne7\).

Ответ: \(\frac{5-y}{5};\ \frac{x+4}{x-4};\ \frac{5-y}{5+y};\ \frac{4-x}{x+4};\ \frac{7-m}{2}\).