25. Сократите дробь: а) (3y + 9)/(y^2 − 9); б) (b^2 − 4)/(6 + 3b); в) (a^2 + 10a + 25)/(3a + 15); г) (x^2 − 9)/(3x^2 + x^3); д) (x^2 − 8x + 16)/(16 − x); е) (y^3 + 27)/(y^2 − 3y + 9).

1. \(\dfrac{3y+9}{y^2-9}=\dfrac{3(y+3)}{(y-3)(y+3)}=\dfrac{3}{y-3}\), \(y
   e\pm3\).
2. \(\dfrac{b^2-4}{6+3b}=\dfrac{(b-2)(b+2)}{3(b+2)}=\dfrac{b-2}{3}\), \(b
   e-2\).
3. \(\dfrac{a^2+10a+25}{3a+15}=\dfrac{(a+5)^2}{3(a+5)}=\dfrac{a+5}{3}\), \(a
   e-5\).
4. \(\dfrac{x^2-9}{3x^2+x^3}=\dfrac{(x-3)(x+3)}{x^2(x+3)}=\dfrac{x-3}{x^2}\), \(x
   e0,-3\).
5. \(\dfrac{x^2-8x+16}{16-x}=\dfrac{(x-4)^2}{-(x-4)}=4-x\), \(x
   e4\).
6. \(\dfrac{y^3+27}{y^2-3y+9}=\dfrac{(y+3)(y^2-3y+9)}{y^2-3y+9}=y+3\).

Ответ: а) \(\dfrac{3}{y-3}\); б) \(\dfrac{b-2}{3}\); в) \(\dfrac{a+5}{3}\); г) \(\dfrac{x-3}{x^2}\); д) \(4-x\); е) \(y+3\).