2. Сократите дроби: \(\frac{a(a-5)}{5a}\), \(\frac{2-d}{(2-d)(2+d)}\), \(\frac{15-3c}{3c}\), \(\frac{-(a-c)}{a-c}\).

1. \(\frac{a(a-5)}{5a}=\frac{a-5}{5}\), при \(a\ne0\).
2. \(\frac{2-d}{(2-d)(2+d)}=\frac1{2+d}\), при \(d\ne2,-2\).
3. \(\frac{15-3c}{3c}=\frac{3(5-c)}{3c}=\frac{5-c}{c}\), при \(c\ne0\).
4. \(\frac{-(a-c)}{a-c}=-1\), при \(a\ne c\).

Ответ: \(\frac{a-5}{5};\ \frac1{2+d};\ \frac{5-c}{c};\ -1\).