Вопрос:

32. Сократите дроби: а) \(\frac{y^2-16}{3y+12}\); б) \(\frac{5x-15y}{x^2-9y^2}\); в) \(\frac{(c+2)^2}{7c^2+14c}\); г) \(\frac{6cd-18c}{(d-3)^2}\); д) \(\frac{a^2+10a+25}{a^2-25}\); е) \(\frac{y^2-9}{y^2-6y+9}\).

Ответ:

  1. \(\frac{y^2-16}{3y+12}=\frac{(y-4)(y+4)}{3(y+4)}=\frac{y-4}{3}\), \(y\ne-4\).

  2. \(\frac{5x-15y}{x^2-9y^2}=\frac{5(x-3y)}{(x-3y)(x+3y)}=\frac{5}{x+3y}\), \(x\ne3y\), \(x\ne-3y\).

  3. \(\frac{(c+2)^2}{7c^2+14c}=\frac{(c+2)^2}{7c(c+2)}=\frac{c+2}{7c}\), \(c\ne0\), \(c\ne-2\).

  4. \(\frac{6cd-18c}{(d-3)^2}=\frac{6c(d-3)}{(d-3)^2}=\frac{6c}{d-3}\), \(d\ne3\).

  5. \(\frac{a^2+10a+25}{a^2-25}=\frac{(a+5)^2}{(a-5)(a+5)}=\frac{a+5}{a-5}\), \(a\ne5\), \(a\ne-5\).

  6. \(\frac{y^2-9}{y^2-6y+9}=\frac{(y-3)(y+3)}{(y-3)^2}=\frac{y+3}{y-3}\), \(y\ne3\).

Ответ: а) \(\frac{y-4}{3}\); б) \(\frac{5}{x+3y}\); в) \(\frac{c+2}{7c}\); г) \(\frac{6c}{d-3}\); д) \(\frac{a+5}{a-5}\); е) \(\frac{y+3}{y-3}\).