Ответ:

  1. \(\frac{y^3}{y^3+y^2}=\frac{y^2\cdot y}{y^2(y+1)}=\frac{y}{y+1}\).
  2. \(\frac{5a^2}{a^4+a^2}=\frac{5a^2}{a^2(a^2+1)}=\frac{5}{a^2+1}\).
  3. \(\frac{x^5+x^3}{x^2+1}=\frac{x^3(x^2+1)}{x^2+1}=x^3\).
  4. \(\frac{b^5-b^4}{b^5}=\frac{b^4(b-1)}{b^5}=\frac{b-1}{b}\).

Ответ: а) \(\frac{y}{y+1}\); б) \(\frac{5}{a^2+1}\); в) \(x^3\); г) \(\frac{b-1}{b}\).