2. Сократите дроби: а) (3c + 9d)/(27(c + 3d)); б) (a² + 16a + 64)/(5a + 40); в) (y² − 144)/(y³ + 12y²).

а) \(\dfrac{3c+9d}{27(c+3d)}=\dfrac{3(c+3d)}{27(c+3d)}=\dfrac{1}{9}\), при \(c+3d\ne0\).

б) \(\dfrac{a^2+16a+64}{5a+40}=\dfrac{(a+8)^2}{5(a+8)}=\dfrac{a+8}{5}\), при \(a\ne-8\).

в) \(\dfrac{y^2-144}{y^3+12y^2}=\dfrac{(y-12)(y+12)}{y^2(y+12)}=\dfrac{y-12}{y^2}\), при \(y\ne0\) и \(y\ne-12\).

Ответ: а) \(\dfrac{1}{9}\); б) \(\dfrac{a+8}{5}\); в) \(\dfrac{y-12}{y^2}\).